The opening verses of Psalm 34 are a cry for God to defend the psalmist, and they include a plea for the defeat of his enemies that resound throughout the psalms of Monday.
St Alphonus Liguori summarises this  psalm as follows:
This psalm is suitable to the just man who, seeing himself exposed here below to the temptations of the devil and to bad treatment on the part of impious men, seeks help from God. This psalm is admirably suited to Jesus Christ, the Just by excellence.
In the Benedictine Office
The placement of Psalm 34 at Monday Matins in the Benedictine Office seems to be important, because some of its key themes are picked up in several other psalms of the day.  
The content of verses 4&5 are
recapitulated first of all in verses 29&30:
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34: 4  Confundántur et
  revereántur,  * quæréntes ánimam meam. 
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4 Let them be confounded and ashamed
  that seek after my soul. 
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5 
  Avertántur retrórsum, et confundántur * cogitántes mihi mala. 
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Let them be turned back and be confounded
  that devise evil
  against me. 
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34: 29  Erubéscant et
  revereántur simul, * qui gratulántur  
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26 Let them blush: and be ashamed together, who rejoice at my evils. 
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30  Induántur confusióne et
  reveréntia * qui magna loquúntur super me. 
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Let them be clothed with confusion and
  shame, who speak great things against me. 
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But the words of verses 4&5 reappear in
virtually identical form in Psalm 39 at Matins:
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39: 19 confundántur et revereántur simul,
  qui quærunt ánimam meam, * ut áuferant eam. 
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15 Let them be
  confounded and ashamed together, that seek after my soul to take it away.  
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20 
  convertántur retrórsum et revereántur: * qui volunt mihi mala. 
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15 Let them be confounded and
  ashamed together, that seek after my soul to take it away.  
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The sentiments are also echoed at Prime in Psalm 6:
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6: 10  Erubéscant, et
  conturbéntur veheménter omnes inimíci mei : * convertántur et erubéscant
  valde velóciter. 
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Let all my enemies be ashamed, and be
  very much troubled: let them be turned back, and be ashamed very speedily. 
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And at Vespers in Psalm 128:
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128: 4  Dóminus justus
  concídit cervíces peccatórum: * confundántur et convertántur retrórsum omnes,
  qui odérunt Sion. 
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4 The Lord who is just
  will cut the necks of sinners: 5 Let them all
  be confounded and turned back that hate Sion.  
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The dust 
imagery of verse 6 is echoed at Prime in Psalm 1:
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34: 6  Fiant tamquam pulvis
  ante fáciem venti: * et Angelus Dómini coárctans eos. 
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5 Let them become as dust before
  the wind: and let the angel of the Lord straiten them. 
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6: 5  Non sic ímpii, non sic: * sed tamquam pulvis, quem prójicit
  ventus a fácie terræ. 
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Not so the wicked, not so: but like the
  dust, which the wind drives from the face of the earth. 
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The text of the psalm
Vulgate 
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Douay-Rheims 
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Ipsi David 
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For David himself 
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Júdica, Dómine, nocéntes me, * expúgna impugnántes me. 
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Judge,
  O Lord, them that wrong
  me: overthrow them that fight against me. 
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Apprehénde
  arma et scutum: * et exsúrge in adjutórium mihi. 
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Take
  hold of arms and shield: and rise up to help me. 
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Effúnde
  frámeam, et conclúde advérsus eos, qui persequúntur me: * dic ánimæ meæ:
  Salus tua ego sum. 
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Bring
  out the sword, and shut up the way against them that persecute me: say to my soul: I am your salvation. 
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Confundántur
  et revereántur,  * quæréntes ánimam meam. 
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Let
  them be confounded and ashamed that seek after my soul. 
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Avertántur retrórsum, et confundántur * cogitántes mihi
  mala. 
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Let
  them be turned back and be confounded that devise evil against me. 
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Fiant
  tamquam pulvis ante fáciem venti: * et Angelus Dómini coárctans eos. 
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Let
  them become as dust before the wind: and let the angel of the Lord straiten them. 
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Fiat
  via illórum ténebræ et lúbricum: * et Angelus Dómini pérsequens eos. 
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Let
  their way become dark and slippery; and let the angel of the Lord pursue them. 
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Quóniam
  gratis abscondérunt mihi intéritum láquei sui: * supervácue exprobravérunt
  ánimam meam. 
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For
  without cause they have hidden their net for me unto destruction: without
  cause they have upbraided my soul 
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Véniat
  illi láqueus, quem ignórat: et cáptio, quam abscóndit, apprehéndat eum: * et
  in láqueum cadat in ipsum. 
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Let
  the snare which he knows not come upon him: and let the net which he has
  hidden catch him: and into that very snare let them fall. 
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Anima autem mea exsultábit in Dómino: * et delectábitur
  super salutári suo. 
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But
  my soul shall rejoice in
  the Lord; and shall be
  delighted in his salvation. 
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Omnia
  ossa mea dicent: * Dómine, quis símilis tibi? 
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All
  my bones shall say: Lord, who is like to
  you? 
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Erípiens ínopem de manu fortiórum ejus: * egénum et
  páuperem a diripiéntibus eum. 
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Who
  delivers the poor from the hand of them that are stronger than he; the needy
  and the poor from them that strip him. 
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Surgéntes testes iníqui, * quæ ignorábam interrogábant
  me. 
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Unjust
  witnesses rising up have asked me things I knew not. 
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Retribuébant mihi mala pro bonis: * sterilitátem ánimæ meæ. 
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They
  repaid me evil for good: to the depriving me of my soul. 
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Ego autem cum mihi molésti essent, * induébar cilício. 
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But
  as for me, when they were troublesome to me, I was clothed with haircloth. 
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Humiliábam
  in jejúnio ánimam meam: * et orátio mea in sinu meo convertétur. 
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I
  humbled my soul with fasting; and my prayer shall be turned into my bosom. 
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Quasi
  próximum, et quasi fratrem nostrum, sic complacébam: * quasi lugens et
  contristátus, sic humiliábar. 
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As
  a neighbour and as an own brother, so did I please: as one mourning and
  sorrowful so was I humbled.  
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Et
  advérsum me lætáti sunt, et convenérunt: * congregáta sunt super me flagélla,
  et ignorávi. 
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But
  they rejoiced against me, and came together: scourges were gathered together
  upon me, and I knew not. 
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Dissipati
  sunt, nec compúncti, tentavérunt me, subsannavérunt me subsannatióne: * frenduérunt
  super me déntibus suis. 
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They
  were separated, and repented not: they tempted me, they scoffed at me with
  scorn: they gnashed upon me with their teeth. 
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Dómine, quando respícies? * restítue ánimam meam a
  malignitáte eórum, a leónibus únicam meam. 
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Lord, when will you look upon me? Rescue
  my soul from their
  malice: my only one from the lions. 
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Confitébor tibi in ecclésia magna, * in pópulo gravi
  laudábo te. 
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I
  will give thanks to you in a great church; I will praise you in a strong
  people. 
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Non
  supergáudeant mihi qui adversántur mihi iníque: * qui odérunt me gratis et
  ánnuunt óculis. 
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Let
  not them that are my enemies wrongfully rejoice over me: who have hated me without cause, and wink with
  the eyes. 
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Quóniam
  mihi quidem pacífice loquebántur: * et in iracúndia terræ loquéntes, dolos
  cogitábant. 
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For
  they spoke indeed peaceably to me; and speaking in the anger of the earth they devised guile.  
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Et
  dilatavérunt super me os suum: * dixérunt: Euge, euge, vidérunt óculi nostri. 
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And
  they opened their mouth wide against me; they said: Well done, well done, our
  eyes have seen it.  
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Vidísti,
  Dómine, ne síleas: * Dómine, ne discédas a me. 
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You
  have seen, O Lord, be not silent:
  O Lord, depart not from
  me. 
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Exsúrge
  et inténde judício meo: * Deus meus, et Dóminus meus in causam meam. 
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Arise,
  and be attentive to my judgment: to my cause, my God, and my Lord. 
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Júdica
  me secúndum justítiam tuam, Dómine, Deus meus, * et non supergáudeant mihi. 
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Judge
  me, O Lord my God according to your justice, and let them not rejoice over
  me. 
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Non
  dicant in córdibus suis: Euge, euge, ánimæ nostræ: * nec dicant: Devorávimus
  eum. 
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Let
  them not say in their hearts: It is well, it is well, to our mind: neither
  let them say: We have swallowed him up. 
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Erubéscant
  et revereántur simul, * qui gratulántur malis meis. 
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Let
  them blush: and be ashamed together, who rejoice at my evils. 
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Induántur
  confusióne et reveréntia * qui magna loquúntur super me. 
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Let
  them be clothed with confusion and shame, who speak great things against me. 
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Exsúltent
  et læténtur qui volunt justítiam meam: * et dicant semper: Magnificétur
  Dóminus qui volunt pacem servi ejus. 
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Let
  them rejoice and be glad, who are well pleased with my justice, and let them say always: The Lord be magnified, who delights in the
  peace of his servant. 
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Et
  lingua mea meditábitur justítiam tuam, * tota die laudem tuam. 
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And
  my tongue shall meditate your justice, your praise all the day long. 
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NT
  references 
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Rom 1:9, 1 Thess 5:1-3
  (9); Lk 1:46 (10); Mt 26:59ff (11);  
Jn 10:32 (14); Jn 15:25
  (22); Jn 20:28 (26) 
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RB
  cursus 
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Monday I, 3 
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Monastic/(Roman)
  feasts etc 
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  |
Roman
  pre 1911 
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Monday Matins 
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Roman
  post 1911 
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1911-62: Tuesday
  Matins  . 1970:  
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Mass
  propers (EF) 
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Passion Friday GR (23, 25);  
Holy Monday, IN (1-3), GR (3, 26), CO (29);  
Holy Tuesday, GR (1-2, 15) 
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