John Gill Commentary Exodus 12:25

"And it shall come to pass, when ye are come to the land which Jehovah will give you, according as he hath promised, that ye shall keep this service." — Exodus 12:25 (ASV)

And it shall come to pass, when you be come to the land To the land of Canaan, towards which they were just about to set forward on their journey, and in a few years would be in the possession of:

which the Lord will give you according as he has promised ; to their fathers, Abraham, Isaac, and Jacob, and to them:

that you shall keep this service ; enjoined them, respecting the passover lamb, and leavened bread, with all the rites and ceremonies relative thereunto, excepting such as were peculiar to the first passover in Egypt.