Why is a little false teaching compared to leaven?
A little false teaching is compared to leaven because yeast does not affect only part of the dough; it spreads through all of it. In the same way, a small amount of false teaching permeates the whole, one error leads to another, and eventually leavens all of Christianity.
Les teaches that leaven is yeast, and when yeast is put into dough it does not leaven just a fourth of it but leavens all of it. He applies this to false teaching: if you let a little bit of false teaching in as leaven, it is not long until it permeates the whole, and one error leads to another. He points to Christendom in general, saying it has been leavened; things Scripture and Christianity stood against fifty, sixty, or seventy years ago are now part and parcel of everyday experience. He illustrates this with a church that kept accommodating worldly things, opening the door wider until you cannot tell the difference between the church and the world. So a little leaven leavened the whole lump. Yet Paul did not give up on these people; he still had confidence and trusted God to bring them back to the truth.
A little leaven leaveneth the whole lump.
More Questions
What is leaven in everyday terms and how does yeast work in dough?
In common vernacular leaven is yeast, and when yeast is put into dough it does not leaven just a fourth of it but leavens all of it.