Why did the Israelites have to eat the Passover lamb?
The Israelites ate the Passover lamb to gain strength for their journey out of Egypt. The lamb's blood on the doorposts secured them from the death angel, and by faith they knew they were safe. Eating the roasted lamb provided physical sustenance for the departure.
Les explains that as the Jewish families stood in their hovels, they were to stand around the kitchen table with the Passover lamb roasted and partake of it to give them strength for their journey. The emphasis is that when they knew the blood was on the doorpost, they did not shake with fear, because by faith they knew the blood had kept them secure, and the death angel would not strike them. Paul later writes in I Corinthians 9 that Christ was our Passover, and if there is a Passover lamb, there must be blood, because the whole idea was the shedding of the lamb's blood so it could be struck on the doorpost.