The responsories for the second Nocturn of Tenebrae for Maundy Thursday, which we start on today with a look at Psalm 71 (72), focus on Judas' betrayal and subsequent horrible fate.
Today's psalm, though, first invites us to reflect on just how terrible a crime that betrayal was by reminding us just who Christ is, and why he came as man to us.
Who is Christ?
The sixth century commentator Cassiodorus provides a nice summary of the progression of the psalm in the light of the New Testament:
"The prophet speaks throughout the psalm, pointing to the coming of the Lord Saviour, and clearly manifesting alternately His humanity and His divinity in one and the same person. In the first section he addresses the Father, begging for His Son the role of judging the nations which is known to have been predestined before time began. In the second part he says that at the Lord's judgment the sons of the poor will be saved, and the pride of the devil undoubtedly brought low. He is also seen to indicate in marvellous fashion the birth from the Virgin, by means of certain parallels. In the third part he recounts what blessings have accrued from the holy Spirit and from the Lord Christ born of the virgin Mary. In the fourth section he says that He is to be adored by all kings because He has freed the human race from the power of the devil. In the fifth he proclaims that once seen by human eyes He was the mainstay of believers and an undoubted Source of progress for the just. In the sixth he relates that praises are to be delivered to the eternal Lord with the unanimity of the whole world. In the seventh he delivers with the sweetest devotion a hymn to the Lord Christ.  It is thus obvious that a clear and manifest beginning to the New Testament has been fashioned in the course of this psalm."
Meditation on the kingship of Christ should surely help us to put our own actions in perspective, and help dissuade us from those small betrayals of his we make each day.
Psalm 71
Deus, iudícium tuum regi da: * et iustítiam
  tuam fílio regis. 
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Give to the king your judgment, O God,
  and to the king's son your justice: 
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Iudicáre pópulum tuum in iustítia, * et páuperes
  tuos in iudício. 
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To judge your people with justice,
  and your poor with judgment.  
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Suscípiant montes pacem pópulo: * et colles iustítiam. 
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Let the mountains receive peace for the people: and
  the hills justice.  
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Iudicábit páuperes pópuli, et salvos fáciet fílios
  páuperum: * et humiliábit calumniatórem. 
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He shall judge the poor of the people, and he shall
  save the children of the poor: and he shall humble
  the oppressor 
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Et permanébit cum sole, et ante lunam, * in
  generatióne et generatiónem. 
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And he shall continue with the sun and before the
  moon, throughout all generations.  
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Descendet sicut plúvia in vellus: * et sicut
  stillicidia stillántia super terram. 
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He shall come down like rain upon the fleece; and as
  showers falling gently upon the earth.  
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Oriétur in diébus eius iustítia, et abundántia
  pacis: * donec auferátur luna. 
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In his days shall justice
  spring up, and abundance of peace, till the moon be taken away.  
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Et dominábitur a mari usque ad mare: * et a flúmine
  usque ad términos orbis terrárum. 
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And he shall rule from sea to sea, and from the
  river unto the ends of the earth.  
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Coram illo prócident Æthíopes: * et inimíci eius
  terram lingent. 
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Before him the Ethiopians
  shall fall down: and his enemies shall lick the ground. 
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Reges Tharsis, et ínsulæ múnera ófferent: * reges
  Arabum et Saba dona addúcent. 
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The kings of Tharsis and the islands shall offer
  presents: the kings of the Arabians
  and of Saba shall bring gifts:  
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Et adorábunt eum omnes reges terræ: * omnes gentes
  sérvient ei: 
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And all kings of the earth shall adore
  him: all nations shall serve him.  
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Quia liberábit páuperem a poténte: * et páuperem, cui
  non erat adiútor. 
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For he shall deliver the poor from the mighty: and
  the needy that had no helper.  
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Parcet páuperi et ínopi: * et ánimas páuperum salvas
  fáciet. 
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He shall spare the poor and needy: and he shall save
  the souls of the poor.  
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Ex usúris et iniquitáte rédimet ánimas eórum: * et
  honorábile nomen eórum coram illo. 
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He shall redeem
  their souls from usuries
  and iniquity: and their names
  shall be honourable in his sight.  
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Et vivet, et dábitur ei de auro Arábiæ, † et adorábunt
  de ipso semper: * tota die benedícent ei. 
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And he shall live, and to him shall be given of the
  gold of Arabia, for him they shall always adore:
  they shall bless him all the day.  
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Et erit firmaméntum in terra in summis móntium, † superextollétur
  super Líbanum fructus eius: * et florébunt de civitáte sicut fœnum terræ. 
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And there shall be a firmament
  on the earth on the tops of mountains, above Libanus
  shall the fruit thereof be exalted: and they of the city shall flourish like
  the grass of the earth.  
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Sit nomen eius benedíctum in sæcula: * ante solem
  pérmanet nomen eius. 
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Let his name
  be blessed for evermore: his name
  continues before the sun.  
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Et benedicéntur in ipso omnes tribus terræ: * omnes
  Gentes magnificábunt eum. 
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And in him shall all the tribes of the earth be blessed:
  all nations shall magnify him.  
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Benedíctus Dóminus, Deus Israël, * qui facit mirabília
  solus. 
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Blessed be the Lord,
  the God of Israel, who alone does wonderful things.  
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Et benedíctum nomen maiestátis eius in ætérnum: † et
  replébitur maiestáte eius omnis terra: fiat, fiat. 
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And blessed
  be the name of his majesty for ever: and the whole earth shall be
  filled with his majesty. So be it. So be it. 
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Glória
  Patri, et Fílio, * et Spirítui Sancto. 
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Glory
  be to the Father, and to the Son, and to the Holy Ghost. 
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Tenebrae of Holy Thursday
Nocturn I: Psalms 68, 69, 70
Nocturn II: Psalms 71, 72, 73
Nocturn III: Psalms 74, 75, 76
Lauds: 50, 89, 35, [Ex 15], 146
And for the antiphon and a few verses of the psalm to listen to (note that it goes on with a setting of the responsories).
Other Scriptural and liturgical uses of the psalm
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NT
  references 
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Lk 1:48 (17); Lk 1:68
  (19) 
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RB
  cursus 
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Wednesday Matins 
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Monastic/(Roman)
  feasts etc 
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Nativity; Epiphany;
  Maundy Thurs Tenebrae, II, 1; Trinity 
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Roman
  pre 1911 
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Thursday Matins 
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Roman
  post 1911 
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1911-62: Thursday
  Prime 1970:  
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Mass
  propers (EF) 
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Christ the King, 8, 11 
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