If you couple what I shared about pride being the opposite of humility and lowliness with what SpeakTruth101 shared about pride being equated with such things as haughtiness, arrogance, loftiness, and an exalting of one's self, then I think that you will come to recognize why leaven, which is yeast or baking powder, and which is a rising agent that is used in baking, is symbolic of sin throughout the Bible. In other words, every type of sin is an exalting of our own ways above God's ways, or a rising up of our own wills against the will of God for our lives, or has pride as its foundation.
While on earth, Jesus constantly humbled himself while seeking the will of his Father in prayer, and he therefore only spoke God's words and only did the things which he saw his Father doing. This is the type of humility or lowliness that we ought to be expressing ourselves as those who profess to be followers of Christ, and this is the only way that we can truly remove all leaven or pride from our lives.
1 Corinthians 5:6-8
"It is reported commonly
that there is fornication among you, and such fornication as is not so much as named among the Gentiles, that one should have his father's wife. And
ye are puffed up, and have not rather mourned, that he that hath done this deed might be taken away from among you. For I verily, as absent in body, but present in spirit, have judged already, as though I were present,
concerning him that hath so done this deed, In the name of our Lord Jesus Christ, when ye are gathered together, and my spirit, with the power of our Lord Jesus Christ, To deliver such an one unto Satan for the destruction of the flesh, that the spirit may be saved in the day of the Lord Jesus. Your glorying
is not good. Know ye not that a little leaven leaveneth the whole lump? Purge out therefore the old leaven, that ye may be a new lump, as ye are unleavened. For even Christ our passover is sacrificed for us: Therefore let us keep the feast, not with old leaven, neither with the leaven of malice and wickedness; but with the unleavened
bread of sincerity and truth."
The Corinthians were "puffed up" (envision the work of leaven, or yeast, or baking powder in cookies, or a cake, or bread) in their minds, and, therefore, they did not throw this impenitent man out of their congregation. Had Paul not intervened, and had this man not been removed from the congregation until the time came when he genuinely repented, then the entire congregation would have been "leavened" because "a little leaven leavens the whole lump".
With this understanding before us, what do you think the average church or congregation today looks like in God's eyes?
Personally, I believe that God sees a gargantuan cake, cookie, or loaf of bread (sticking with the analogy), and I doubt that he finds it the least bit appealing or appetizing. In other words, our churches or congregations are loaded with impenitent sinners, thereby "leavening" the whole congregation, and many of the impenitent sinners are standing behind the pulpit.