Now the Passover Festival and the Festival of Unleavened Bread were held two days later. [Note: This was the annual Jewish Festival week commemorating Israel's deliverance from Egyptian bondage under Moses' leadership. The unleavened bread was specially baked bread containing no yeast, which was eaten for seven days as part of the celebration]. And the leading priests and experts in the law of Moses were looking for a way to take Jesus by trickery and kill Him.

And they began reasoning among themselves, saying, "[Why be concerned about yeast since] we did not bring [any] bread?"

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."

Then they understood that He was not telling them to watch out for the yeast in [physical] bread, but for the teaching of the Pharisees and Sadducees.

And they began reasoning with one another, saying, " [Why be concerned about yeast since] we do not have [any] bread?"

So, we should observe the Festival [i.e., live the Christian life], but not with the old yeast [i.e., old sinful ways], such as the leavening [effect] of evil and wickedness, but with the unleavened bread of sincerity and truth.