How Augustine tried to handle the mistake.
We had prepared a brief Psalm for you, which we had told the Lector to chant, but when it came time, he became distracted, it seems, and read another one in its place. We prefer to follow the will of God in the Lector’s mistake than our will and plan. If, then, we keep you for some time because of the Psalm’s great length, don’t blame us, but believe that God has not wanted us to labor unfruitfully. It was not, after all, in vain that we received a punishment for the first sin: that we would eat bread in the sweat of our brow (Gn 3:19). Only consider it is bread. It is bread if it is Christ. “I am,” he said, “the living bread that came down from heaven” (Jn 6:41). And the one made manifest in the Gospel, let us now seek also in the prophets. There they upon whom a veil is still placed, do not see him there (see 2 Cor 3:14)... But because the evening sacrifice of the Lord’s cross has torn the veil open for us and the temple’s secrets have been made known, as long as Christ is preached to us, the bread is to be eaten, even in toil and sweat. (EnPs 138, 1; PL 37, 1784)