Cyril of Alexandria

Having granted to the children of the Bridegroom that it was not fitting that they should be troubled, as they were keeping a spiritual feast, but that fasting should be abolished among them, He adds as a direction, But the days shall come when the Bridegroom shall be taken from them, and then shall they fast in those days.

Catena Aurea by Aquinas ↗

Ambrose of Milan

"But the days will come when the Bridegroom shall be taken from them." Which are these days in which Christ is taken from us, especially when he himself has said, "I shall be with you, even to the end of the world," when he has said, "I will not leave you orphans"? For it is certain that if he were to leave us, we could not be saved. None can take Christ from you, unless you take yourself away. Your boasting will not take you away, nor arrogance, nor may you presume on the law for yourself. …

Commentary on Luke ↗

Bonaventure

And therefore the consolation of the disciples is befitting the presence of the bridegroom Christ, just as also desolation is befitting his absence. On account of which he adds: But the days will come when he will be taken away from them, namely through death and passion: Hosea 5: "They will go to seek the Lord and will not find him: for he has been taken away from them," and then they will fast in those days, namely at that time: because John 16: "You will weep and lament, but the world will rejoice; you indeed will be sorrowful, …

Commentary on Luke, Chapter 5 ↗