Theophylact of Ohrid

The divine teaching "is like leaven, which a woman," that is, human nature, "took and hid in three measures of meal," that is, in body, soul, and spirit, so that all was sanctified, as the blessed Paul says (1 Tim. 4:5), and became one lump of dough through communion with the Holy Spirit. By the woman you may understand the soul, and by the three measures its three powers: the mind, the heart, and the will. …

Commentary on Luke ↗

Augustine of Hippo

Or, the three measures of meal are the race of mankind, which was restored out of the three sons of Noah. The woman who hid the leaven is the wisdom of God.

Catena Aurea by Aquinas ↗

Bonaventure

And since charity and joy dilate and warm the heart from within, and this is the outward likeness with leaven, therefore he adds: It is like leaven. And note that by leaven is sometimes understood the corruption of peace and unity, as above in the twelfth chapter: "Beware of the leaven of the Pharisees, which is hypocrisy"; and this quite rightly, because leaven is old dough, corrupted by age and turned to sourness, which corrupts the remaining mass and turns it to sourness. …

Commentary on Luke, Chapter 13 ↗