The Passover, the most significant feast on the Jewish calendar, commemorated Israel’s deliverance from Egypt, and so the Lord told Israel to observe the Passover on the 14th day of the month,

Now you shall keep it until the fourteenth day of the same month. Then the whole assembly of the congregation of Israel shall kill it at twilight (Exodus 12.6). 

Fourteen is a multiple of seven and no doubt signified the Lord’s perfect redemption of Israel.

Thanks to Karen Crawley for pointing out this significant event that I had missed.