“On the evening of the fourteenth day of the month, while camped at Gilgal on the plains of Jericho, the Israelites celebrated the Passover. The day after the Passover, that very day, they ate some of the produce of the land: unleavened bread and roasted grain. The manna stopped the day after they ate this food from the land; ... “(Josh 5:10-12).
The first Passover celebrated when Israel entered the Promised Land was a Thanksgiving week to God for His faithfulness to them. The Passover initially was a kind of covering or substitution that God required of them so that He would pass over every first born of the Israelites and their cattle.