Bede

Taking occasion then from the precept, which He had commanded, saying, Beware of the leaven of the Pharisees and of the leaven of Herod, our Saviour teaches them what was the meaning of the five and the seven loaves, concerning which He adds, And do ye not remember, when I brake the five loaves amongst five thousand, and how many baskets full of fragments ye took up? For if the leaven mentioned above means perverse traditions, of course the food, with which the people of God was nourished, means the true doctrine.

Catena Aurea by Aquinas ↗