(6) Your boasting is not good. Don't you know that a little yeast works through the whole batch of dough? (7) Get rid of the old yeast that you may be a new batch without yeast- as you really are. For Christ, our Passover lamb, has been sacrificed. (8) Therefore let us keep the Festival, not with the old yeast, the yeast of malice and wickedness, but with bread without yeast, the bread of sincerity and truth. (1 Corinthians 5:6-8)
As it says in verse 8, the yeast here represents "malice and wickedness"- in other words, sin and bad intentions. And, just like the yeast in a batch of dough, sin has a tendency to spread and pervade every part of your life; and bad intentions will taint your actions until everything you do has a selfish motive. But verse 7 tells us to get rid of the "old" yeast- it's old because malice and wickedness are associated with the sinful nature, which you put to death when you accepted Christ. In so doing we become a new batch, a new creation, without the sinful nature's contagious yeast. We become as we really are: sanctified.
And without that yeast, you're a totally different batch of bread. Without malice in your heart, you can love people in a way that is real, unconditional, and completely selfless. Malice makes kindness impossible and honesty irrelevant; but without it, you become a vessel for God to lavish love on His people. As for wickedness, it's the defiance of God's truth; it's knowing what He commands but choosing to sin anyway. When you remove that wickedness from your life and your actions, not only are you obeying the truth, but you're putting it on display to those around you. Without that yeast, you're a delicious loaf of sincerity and truth.
Read also Luke 12:1-2.
