The Canonical Epistle, with the Commentaries of Theodore Balsamon and John Zonaras 15Canon XV.

No one shall find fault with us for observing the fourth day of the week, and the preparation, on which it is reasonably enjoined us to fast according to the tradition. On the fourth day, indeed, because on it the Jews took counsel for the betrayal of the Lord; and on the sixth, because on it He himself suffered for us. But the Lord's day we celebrate as a day of joy, because on it He rose again, on which day we have received it for a custom not even to bow the knee.