Mark 8:15
Then Jesus ordered them, saying, "Pay attention and watch out for the leavening [effect] of the Pharisees and Herod." [Note: By "Herod" is probably meant the Herodians, who were a party favorable to King Herod and, along with the Pharisees and Sadducees, were out to get Jesus. See Matt. 16:6].
Luke 12:1
About this time, while a crowd of many thousands had assembled, [so large that] people were trampling on one another, Jesus first began telling His disciples, "Watch out for the leavening [effect] of the Pharisees, which is hypocrisy.
Galatians 5:9
A little bit of yeast permeates the whole batch of dough [i.e., a few people can influence everyone else to do the wrong thing in this matter].
Matthew 16:6
Jesus said to them, "Pay attention and watch out for the leavening [effect] of the Pharisees and Sadducees."
Matthew 16:11-12
How is it that you do not understand that I was not speaking to you about [physical] bread? But [rather I meant] watch out for the yeast [i.e., the influence] of the Pharisees and Sadducees."
Luke 21:34
"But pay attention to yourselves so that your hearts do not become overburdened by carousing, and drunkenness, and the worries of life. [If you do], that 'day' [i.e., Jesus' second coming and judgment] will arrive suddenly, like a trap [i.e., which catches an animal by surprise].
Acts 14:22
[Along the way] they strengthened the hearts of the disciples, urging them to continue [to believe and practice] the faith and [explaining] that entering God's [heavenly] kingdom [See II Tim. 4:18] requires enduring many trials.
1 Corinthians 5:6-8
Your boasting is not good. Do you not know that a little yeast can leaven the whole batch of dough?
1 Peter 4:2
So then, you should no longer live the rest of your lives [to satisfy] the sinful desires of your body, but to do what God wants.