Exodus 13:14
And it shall be when thy son asketh thee in time to come, saying, What is this? that thou shalt say unto him, By strength of hand the LORD brought us out from Egypt, from the house of bondage: And it shall be when thy son asketh thee in time to come, saying, What is this? that thou shalt say unto him, By strength of hand the LORD brought us out from Egypt, from the house of bondage:
The instruction anticipates a future day when a son asks what the observance means, and it directs the parent to answer that with mighty power the Lord brought His people out of Egypt, out of the house of bondage. That mighty deliverance was shown in action at the crossing of the Red Sea, where God Himself led Israel and stood between them and the Egyptians to protect them. There He opened a way through the sea and saved Israel while the pursuing Egyptian army perished in the waters. The command is carried out in the practice of paying a redemption price for each first-born son. The setting apart of the first-fruits and the first-born taught Israel to put God first and to remember that all they possessed belonged to Him.