St. Athanasius of Alexandria ca. 293-373
For what is so fitting for the feast, a turning from wickedness, and a pure conversation, and prayer offered without ceasing to God, with thanksgiving? Therefore let us, my brethren, looking forward to celebrate the eternal joy in heaven, keep the feast here also, rejoicing at all times, praying incessantly, and in everything giving thanks to the Lord. I give thanks to God, for those other wonders He has done, and for the various helps that have now been granted us, in that though He has chastened us sore, He did not deliver us over to death, but brought us from a distance even as from the ends of the earth, and has united us again with you. I have been mindful while I keep the feast, to give you also notice of the great feast of Easter, that so we may go up together, as it were, to Jerusalem, and eat the Passover, not separately but as in one house ; let us not as sodden in water, water down the word of God; neither let us, as having broken its bones, destroy the commands of the Gospel. But as roasted with fire, with bitterness, being fervent in spirit, in fastings and watchings, with lying on the ground, let us keep it with penitence and thanksgiving.
We begin the fast of forty days on the sixth day of Phamenoth; and having passed through that properly, with fasting and prayers, we may be able to attain to the holy day. For he who neglects to observe the fast of forty days, as one who rashly and impurely treads on holy things, cannot celebrate the Easter festival. Further, let us put one another in remembrance, and stimulate one another not to be negligent, and especially that we should fast those days, so that fasts may receive us in succession, and we may rightly bring the feast to a close. (Letters 19.8-9)