Psalm 118 (119), at 176 verses, is the longest in the psalter, and an important one, devoted to the praise of the law.
It is neatly divided into twenty-two stanzas of eight verses, and in Hebrew it is one of the alphabetic psalms, presumably to facilitate memorization.
Psalm 118 in the Office
In the older form of the Roman Office, it was said daily, from Prime to None.
St Benedict, however, spreads it over Sunday and Monday in his form of the Office. One can perhaps view this as in juxtaposition to his use of the Gradual Psalms for the remainder of the week: the law (Psalm 118) is a necessary foundation for the ascent of grace (Psalms 119-133).
Many verses of the psalm are used in Mass propers, and it has much in it that makes it worth meditating on at any time, as well as in the context of the Office.
As a Lenten devotion
The series below, however, was written as a Lenten series.
Saying Psalm 118 daily as a Lenten penance has some tradition behind it, for a letter found in a medieval manuscript purporting to be from St Scholastica to a fellow abbess, which details the Lenten practices at her monastery says that:
"Nonna Marcellina asked me if she might pray the Beati immaculati (Psalm 118) daily through Lent. She knows it by heart, of course."
The links below show how the psalm is allocated between the hours of the Benedictine Office.
(Introduction to Psalm 118 Pt 1, Part II, Part III & Part IV)
Psalm 118 (Aleph) - Beati immaculati
Psalm 118 (Beth) - In quo corrigit
Psalm 118 (Ghimel) - Retribue servo tuo
Psalm 118 (Daleth) - Adhaesit pavimento anima mea &vs 32 (cum dilatasti cor meum)
Psalm 118 (He) - Legem pone mihi
Psalm 118 (Vau) - Et veniet super misericordia tua Domine
Psalm 118 (Zain) - Memor esto verbi tui servo tuo & Vs 52-56:Cantabiles mihi
Psalm 118 (Heth) - Portio mea Domine & Verses 63&64: Particeps ego sum
Psalm 118 (Teth) - Bonitatem fecisti cum servo tuo Domine
Psalm 118 (Jod) - Manus tuae fecerunt me
Psalm 118 (Caph) - Deficit in salutare tuum anima mea
Psalm 118 (Lamed) - In aeternum Domine
Psalm 118 (Mem) - Quomodo dilexi legem tuam Domine