As we enter the last few days of Lent, and start the sacred Triduum, I thought I would end this series by providing a few sources to stimulate meditation that pull the whole set of psalms together in various ways.
To start with, here is Cassiodorus' summary of the fifteen steps represented by each psalm (I've inserted notes on which hour they are said at in the Benedictine Office):
On the first step he denotes loathing of the world, after which there is haste to attain zeal for all the virtues.
Secondly, the strength of divine protection is explained, and it is demonstrated that nothing can withstand it.
Thirdly, the great joy of dwelling with pure mind in the Lord's Church is stated.
Fourth, he teaches us that we must continually presume on the Lord's help whatever the constraints surrounding us, until He takes pity and hears us.
Fifth, he warns us that when we are freed from dangers, we must not attach any credit to ourselves, but attribute it all to the power of the Lord.
In the sixth, the trust of the most faithful Christian is compared to immovable mountains.
In the seventh, we are told how abundant is the harvest reaped by those who sow in tears.
In the eighth, it is said that nothing remains of what any individual has performed by his own will; only the things built by the sponsorship of the Lord are most firmly established.
In the ninth, it is proclaimed that we become blessed through fear of the Lord, and that all profitable things are granted us.
In the tenth, he inculcates in committed persons the patience which he commands through the words of the Church.
In the eleventh, as penitent he cries from the depths to the Lord, asking that the great power of the Godhead be experienced by the deliverance of mankind.
In the twelfth, the strength of meekness and humility is revealed.
In the thirteenth, the promise of the holy incarnation and the truth of the words spoken are demonstrated.
In the fourteenth, spiritual unity is proclaimed to the brethren, and to them the Lord's benediction and eternal life are shown to accrue.
In the fifteenth, there is awakened in the course of the Lord's praises that perfect charity than which nothing greater can be expressed, and nothing more splendid discovered. As the apostle attests: God is love. So let us continually meditate on the hidden nature of this great miracle, so that by ever setting our gaze on such things, we may avoid the deadly errors of the world.
The number of these psalms contains this further mystery: when the five bodily senses, by which human frailty incurs all sin, are overcome by the power of the Trinity, this leads us to the fifteenth height of the psalms of the steps; thus the body's weakness is eliminated, and eternal rewards are bestowed on those who conquer it.