Useful and necessary
Cassian said, “We came from Palestine to Egypt, and visited one of the hermits. After he had welcomed us, we asked him, “When you receive guests, why don’t you fast? In Palestine they do.”
He answered, “Fasting is always possible but I cannot keep you here for ever. Fasting is useful and necessary, but we can choose to fast or not fast. God’s law demands from us perfect love. I receive Christ when I receive you, so I must do all I can to show you love. When I have said goodbye to you, I can take up my rule of fasting again. “The sons of the bridegroom cannot fast while the bridegroom is with them; when he is taken from them, then they can fast” (Matt 9:15).”‘
– De vitis Patrum, Sive Verba Seniorum, Liber V