SIX PSALMS - (Hexapsalmos) The suite of six psalms read at the start of Matins: Psalms 3, 37 (38), 62 (63), 87 (88), 102 (103), and 142 (143). Matins begins with the reading of the "Six Psalms," i.e. Psalms 3, 37, 62, 87, 102, and 142, read in that order, and combined into a single whole.
The faithful should be aware of the fact that the reading of the "Six Psalms" is one of the most important points in [Matins or] the All-night Vigil, a time when all should put aside other thoughts, stand quietly, and concentrate on these penitential prayers.
The Six Psalms comprise an entire scale of experiences which illumine the Christian life of the New Testament - not merely its overall joyous mood, but also the sorrowful path to that joy.
This is why according to the rubrics of the Church, the candles in the church are to be extinguished. The falling darkness symbolizes that dead of night during which Christ, praised in the angelic song "Glory to God in the Highest," came to earth. The semi-darkness of the church facilitates great prayerful concentration. [Esp. Russian practice at All-Night Vigil.]
Midway through the Six Psalms, at the beginning of the 4th of the psalms, the one most filled with sorrow and extreme bitterness, the priest leaves the Altar and, standing before the [icon of Christ or] Royal Doors, continues to quietly read the 12 appointed morning prayers. At that point, the priest symbolizes Christ, who, having heard the sorrow of fallen mankind, not only descended, but to the very end also shared in the suffering of which Psalm 87 speaks.
The morning prayers quietly read by the priest include prayers for the Christians standing in the church, with requests that they be forgiven their sins, that they be given true faith and sincere love, that all of their works be blessed, and that they be made worthy of the Kingdom of Heaven.