God was about to bring his people out of Egypt, and he was giving them instructions about what they should do on that day and again later as they remembered that day. Alternate translation: "because it is on this day that I will have brought your hosts out of the land of Egypt" or "for it will remind you that it was on this day that I brought your hosts out of the land of Egypt"
A host is a military term referring to a large number of soldiers. God speaks of the many people of Israel as if they were an army of many soldiers. Alternate translation: "your armies" or "your tribes" (See: [[rc://en/ta/man/jit/figs-metaphor]])