When the lord shall bring you into the land, thou shalt keep this service — 'Till then they were not obliged to keep the passover, without a particular command from God.
Related Commentaries of Exodus 13:5
Exodus 13:5
5 And it shall be when the LORD shall bring thee into the land of the Canaanites, and the Hittites, and the Amorites, and the Hivites, and the Jebusites, which he sware unto thy fathers to give thee, a land flowing with milk and honey, that thou shalt keep this service in this month.