What is the meaning of spiritual leaven in 1 Corinthians 5:7? "Get rid of the old yeast, so that you may be a new unleavened batch."

The yeast is frecuently spoken in the New Testament, the first letter to the Corinthians tells us: "Get rid of the old yeast, so that you may be a new unleavened batch", 1 Corinthians 5:7
The leaven or the yeast is the "fermental teaching", in the gospel the wisdom (the knowledge of the correct means to live) is the fermental teaching, because is progressive.

Paul tells us of an old leaven, that is, the Law of Moses, and the new, progressive, that comes from the kingdom of God. Jesus considers the teachings of the Pharisees heretical, so he tells us about the old leaven, an example of the old leaven is the Law of Talion:
"You have heard that it was said that it was said, "Eye for eye, and tooth for tooth". But I tell you, do not resist an evil person. If anyone slaps you on the right cheek, turn to them the other cheek also. And if anyone wants to sue you and take your shirt, hand over your coat as well. If anyone forces you to go one mile, go with them two miles. Give to the one who asks you, and do not turn away from the one who wants to borrow from you" Matthew 5:38-42
In this case, the new leaven is the mercy (compassion, affability, amability, benevolence) which is contrary to the Law of Talion (old leaven).
Heresy (teaching of the error) and wisdom are opposite, and fermental because they produce fruit, wisdom produces the fruit of life ( "But the fruit of the spirit is love, joy, peace, forbearance, kindness, goodness,faithfulness, gentleness, self-control. Against such things there is no law", Galatians 5:22-23), heresy produces the fruit of death ("The acts of the flesh are obvious: sexual immorality, impurity and debauchery; idolatry and witchcraft; hatred, discord, jealousy, fits of rage, selfish ambition, dissension, factions and envy, drunkenness, orgies and the like . I warn you, as I did before, that those who live like this will not inherit the kingdom of God." Galatians 5:19-21)
Jesus warns us about the old leaven:
"Leave them; they are blind guides. If the blind lead the blind, both will fall into a pit", Matthew 15:14; also "Meanwhile, when a crowd of many thousands had gathered, so that they were trampling on one another, Jesus began to speak first to his disciples, saying: ´Be on your guard against the yeast of the Pharisees, which is hypocrisy.´" Luke 12:1
We choose between the old and the new leaven.
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