Ambrose of Milan
Catena Aurea · Lukasevangelium 5
And they said unto him, Why do the disciples of John fast often, and make prayers, and likewise the disciples of the Pharisees; but thine eat and drink? And he said unto them, Can ye make the children of the bridechamber fast, while the bridegroom is with them? But the days will come, when the bridegroom shall be taken away from them, and then shall they fast in those days. And he spake also a parable unto them; No man putteth a piece of a new garment upon an old; if otherwise, then both the new maketh a rent, and the piece that was taken out of the new agreeth not with the old. And no man putteth new wine into old bottles; else the new wine will burst the bottles, and be spilled, and the bottles shall perish. But new wine must be put into new bottles; and both are preserved. No man also having drunk old wine straightway desireth new: for he saith, The old is better.
Lastly, it is spoken of the fast of the soul, as the context shews, for it follows, But he said, No man putteth a piece of a new garment upon an old. He calleth fasting an old garment, which the Apostle thought should be taken off, saying, Put off the old man with his deeds. (Col. 3:9.) In the same manner we have a series of precepts not to mix up the actions of the old and new man.