The words "the Feast of" are not in the Hebrew of verse 17, but were added by the translators. God says here that His people are to keep the annual practice of deleavening because He brought His Old Testament church out of Egypt (verse 39). We find later that this great and miraculous event symbolized freeing His New Testament church from sin. Many scriptures show that both Egypt and leaven are symbols of sin.
Did God really intend His people to observe this practice forever, as we read in verse 17, or was it nailed to the cross of Jesus Christ? These three scriptures from the early church after Jesus' crucifixion show that it is indeed a New Testament practice:
» And because he saw that it pleased the Jews, [Herod] proceeded further to seize Peter also. Now it was during the Days of Unleavened Bread. (Acts 12:3)
» But we sailed away from Philippi after the Days of Unleavened Bread. . . . (Acts 20:6)
» Your glorying is not good. Do you not know that a little leaven leavens the whole lump? Therefore purge out the old leaven, that you may be a new lump, since you truly are unleavened. For indeed Christ, our Passover, was sacrificed for us. Therefore let us keep the feast, not with old leaven, nor with the leaven of malice and wickedness; but with the unleavened bread of sincerity and truth. (I Corinthians 5:6-8)
We know that Jesus kept the Feast of Unleavened Bread, and perhaps what is more important for our example, these scriptures prove that His early New Testament church kept it after His death, resurrection, and ascension.
The Five Ws of Deleavening