Now there are two fasts, one is in tribulation, to propitiate God for our sins; another in joy, when as carnal things delight us less, we feed the more on things spiritual. The Lord therefore being asked why His disciples did not fast, answered as to each fast. And first of the fast of tribulation; for it follows, And he said unto them, Can ye make the children of the bridegroom fast when the bridegroom is with them?
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: de Qu. Ev. l. ii. q. 18.