Exegetes have varied interpretations of the parable. Some say that the leaven is a positive image, showing the Christian faith transforming society. The idea that it concerns the church and its gradual growth is unlikely (see Matthew 13:32). Seeing the dough as a symbol of society is also uncertain. Others note that, for Jews at Passover, leaven often symbolizes evil (1 Corinthians 5:6–8; see Matthew 16:6, Matthew 16:12; Mark 8:15), so some say that the woman was preparing a grain offering, for which leaven was forbidden (Leviticus 2:11; Judges 6:18–19), with Jesus warning against the spread of a false church through the power of corrupt teaching. Yet symbols can be used both positively and negatively (like the serpent in Matthew 10:16, or images like water and fire). The claim that the scene is a grain offering is uncertain.
Exegetes differ when it comes to the interpretation of the parable of the leaven. Some hold that the leaven serves as an image of a positive force and that the parable means the Christian faith will permeate and transform all of society. The idea, however, that it primarily concerns the church and gradual ecclesial growth is unlikely (see Matthew 13:32). Likewise, understanding the dough as a symbol of society is uncertain. Others note that, for Jews in the context of Passover, leaven often symbolizes evil (1 Corinthians 5:6–8; see also Matthew 16:6, Matthew 16:12; Mark 8:15). In that connection some suggest the woman was preparing a grain offering, for which leaven was forbidden (Leviticus 2:11; Judges 6:18–19). Such a reading would entail that the parable is warning against the spread of a false church through the power of corrupt teaching. Yet symbols can be used both positively and negatively (for example, serpent in Matthew 10:16, or images like water and fire). The claim that the scene depicts a grain offering is, at best, uncertain.1
It is most likely that the parables of the mustard seed and the yeast were paired because they conveyed the same message—thereby forming a kind of twin parable. In any case, just as with the mustard seed, this parable contrasts the beginning—the tiny bit of yeast—with the end, the surprisingly large amount of risen dough. It is not about the fermentation process, which is invisible and happens throughout the night. Our attention is directed more to the image of the risen dough, which represents the kingdom of heaven, rather than to the yeast itself (like the tree-image in the previous parable). Dough is sometimes used as a symbol for the people of God (Romans 11:16). The meaning here is that just as surely as a small piece of yeast produces a whole batch of risen dough, so the small company of Jesus’ disciples will, in that particular moment, when the Lord comes in glory, become a universal people of God.2
32 It is the smallest of all seeds, but when it has grown it is larger than all the garden plants and becomes a tree, so that the birds of the air come and make nests in its branches.”