Sometimes the simplest answers are the best. I’ve asked again and again why it was that, thirty years after the ascension of Christ—long after everything that was nailed the cross was nailed there—a gentile church was observing the Passover and the days of unleavened bread that go along with it? Well, the simple answer is that the Passover and the Days of Unleavened Bread are all about Christ.
It was Paul who said it in his first letter to the Corinthians.
Your boasting is not good. Do you not know that a little leaven leavens the whole lump of dough? Clean out the old leaven, that you may be a new lump, just as you are in fact unleavened. For Christ our Passover also has been sacrificed. Let us therefore celebrate the feast, not with old leaven, nor with the leaven of malice and wickedness, but with the unleavened bread of sincerity and truth.
According to Paul, the Passover and the days of unleavened bread are about Christ. But how so?