Hag HaMatzoh (Feast of Unleaven Bread) celebrates that Yeshua, like the matzoh we eat, was without leaven (sin). Therefore only unleaven bread, matzoh, is eaten for the next 7 days following Pesach, in the feast called Unleaven Bread. It is to remember the Hebrews and their rushed escape from Egypt, where they didn't have time to wait for their bread to rise. It also recalls their years of wandering in the desert.
The third day after Pesach is called Sfirat Haomer (First Fruits). It is also the day Yeshua was resurrected as the First Fruits of the brethren. In the time of the Temple, First Fruits as a thanksgiving celebration for the early barley harvest. The priests were to wave a sheaf of barley before the Lord in a First Fruits offering. This would allow for the consumption of the rest of the early harvest.
Not only is Yeshua our Passover Lamb, He is our sinless sacrifice, and He is the first fruits of the resurrection. Because He lives, we too will live.