God’s plan was to rescue the children of Israel, lead them to the promised Land, and that is where they would begin to establish His laws. That is why He tells them to start holding this annual feast of the Passover when they get to the promised land. Unfortunately, the people will rebel in a later chapter, and not enter the land. But that will not exempt them from celebrating their deliverance from Egypt. It is so important that this annual memorial is held that it will be done before God’s plan is executed as ordered.
Likewise, we have been redeemed, as the first born sons, by the substitutionary death of the lamb. And we are all to remember this with the annual Passover feast. And we are to receive the promises of God. Even if we fail to walk in those promises, we are still His sons, male and female alike, if we remember Him and what He did for us. If we forget Him, we are cut off. If we hold fast to Him, we are always His children, even if we do not experience our promised land, which is out life here on Earth, not in heaven.