Israel’s greatest need under the old covenant was to remember the great salvation God brought to them when He called them out of Egyptian slavery. Consequently, Passover, the feast celebrating that redemption, was the most important festival on their calendar. Today’s passage records the very first Passover.
The context in which this first Passover was celebrated was the tenth and final plague on Egypt — the death of the firstborn (Ex. 11). One of the main purposes of the first Passover was to provide a way for the children of Israel to escape the angel of death that would be going throughout the land on that night. We know this to be the case because of the requirement that the Israelites mark the lintels and doorposts of their homes with the blood of lambs (12:21–28). God certainly did not need this marking to tell His people apart from the Egyptians, so the need for the sign points to a deeper theological reality. Judgment would be passing through the land indiscriminately; every family was subject to the punishment that would be meted out, even the Israelites. There was nothing inherent in them that made them any less worthy of death than their Egyptian oppressors. Marking the door with blood signified that death had already taken place in that household — judgment had been meted out there, albeit on a substitute victim. The angel could thus pass over that home without inflicting harm. It was a sign to the Israelites that they too were sinners deserving of death but had a way to escape destruction through the Almighty’s grace.
Along with the placing of blood on the doors, Israel was also to avoid all leaven (vv. 18–20). In Scripture, leaven is symbolic of a pervasive influence. Here, though not in every part of the Bible, the pervasive influence being symbolized is sin. In being redeemed from Egyptian slavery, the Israelites were also to rid themselves of the evil, idolatrous ways of the Egyptians. There could be no compromise, for just as it takes merely a pinch to leaven an entire loaf of bread, so too allowing one small sin would corrupt the entire person and nation. “A little leaven leavens the whole lump” (Gal. 5:9), and salvation by grace alone brings with it the responsibility for God’s people to mortify sin and, relying on the strength of the Holy Spirit, fight to the death against its destructive presence and influence.