The Hexapsalmos' are the Six Psalms that are read after the apolysis of the Mesonyktikon.
The Priest comes into the holy Sanctuary, and standing before the Holy Table makes the ekphonesis with reverence and the fear of God, Blessed is our God; the Reader says the Trisagion; the Priest, the For Thine is the kingdom; the Reader, the troparia Save, O Lord, Thy people, Glory, Thou who wast lifted up on the Cross, Both now, Awesome protection, the Priest, Have mercy on us, O God etc., the ending, For Thou art a merciful God… and the Reader, In the name of the Lord, Father, bless; the Priest, Glory to the Holy and Consubstantial…, etc., the Proïstamenos says the Hexapsalmos with compunction while the people listen in total silence and reverence. The Hexapsalmos are never left out, save the Week of New Creation and the day of the leave-taking of Pascha.
Psalms 3 is read for the "Help for the Afflicted" Psalms 37 (38) is a psalm of repentance. Psalms 87 (88) is a remembrance of the Darkness of death. Psalms 102 (103) is a praise for mercy and for the Angelic hosts. In Psalm 142 (143), we wait in darkness for the Light.