The Canons of the Council in Trullo; Often Called The Quinisext Council 90Canon XC.

We have received from our divine Fathers the canon law that in honour of Christ's resurrection, we are not to kneel on Sundays. Lest therefore we should ignore the fulness of this observance we make it plain to the faithful that after the priests have gone to the Altar for Vespers on Saturdays (according to the prevailing custom) no one shall kneel in prayer until the evening of Sunday, at which time after the entrance for compline, again with bended knees we offer our prayers to the Lord. For taking the night after the Sabbath, which was the forerunner of our Lord's resurrection, we begin from it to sing in the spirit hymns to God, leading our feast out of darkness into light, and thus during an entire day and night, we celebrate the Resurrection.