Feast of unleavened bread

The Feast of unleavened bread is written also from the Old and New Testament what is the feast of unleavened bread will the Lord command is real to eat unleavened bread for 7 days doing his time to pass over the wave offering in the last night are three major holidays that take place during the week of unleavened bread or three or prophetic so why is it a Commandment that we should participate in these things yet and most religious institution that is this a Christian institution don't practice the things that are written so in Jesus name let's research