The opening verses of Leviticus 23 tell us that " Holy Convocation" in the original Hebrew is kodesh mikraw, a sacred rehearsal. God is telling Israel to celebrate or rehearse these Holy holidays to proclaim or reveal Him to the world.
The first was the weekly Sabbath or Shabbat. God created in six days and rested on the seventh...and so should we.
The remaining seven feasts or holidays are annual and the first is Passover or Pesach. Verse 5 tells Israel that on the 14th day of the first month at twilight they are to rehearse the Lord's Passover. The first month in the Jewish calendar is Nisan. The timing was to commemorate Israel's exodus from Egypt.
The Israelites were to put the blood of a lamb on their doorposts so that death would passover them. Remember now, rehearsal can mean a look back, a look forward or both. While the obedient Jew was to use Passover or Pesach as an opportunity to look back at what the Lord did, it was also meant to be a look forward at what the Lord WOULD do, send a NEW passover lamb, whose shed blood would cover their sin, our sin and cause death to passover. Are you covered by the blood of the Passover Lamb?