Where did the food they were to prepare and set aside come from? It could not have been manna because manna spoiled within one day (Exodus 16:20). Besides, fresh manna continued to fall each day, except for Sabbaths, until the day following the First Day of Unleavened Bread in that year. God stopped providing manna because the Israelites now had complete access to the produce of the Promised Land, as well as because they were no longer wandering but were camped at a place from which they would launch their conquest of the land.
Considering the time of year (spring), the provision could not have come from fall harvests of fruits and vegetables. The fleeing Canaanites would have either consumed them themselves by this time or taken as much with them as they could. The provision came from a new spring harvest of grains either of winter wheat or barley or both. There was nothing to stop the Israelites from partaking of what was available because no law of God prohibited it; the offering laws applied only to what Israel had planted.
The command to set aside food was made because God knew He would stop sending the manna on Nisan 16. The stockpiled food would keep Israel fed until a much larger harvest could be made after the Passover events were completed, the holy day observed, and Israel was more settled in the land, preparing for the conquest of Jericho.
Israel crossed the Jordan into the Promised Land on Nisan 10 and immediately moved to set up camp that day in Gilgal. The mass circumcisions mentioned must have taken place on Nisan 11. As Nisan 13 ended and Nisan 14 began, they kept the Passover as commanded by God. The daylight portion of Passover day was spent preparing for the holy day on Nisan 15. They kept the Night to be Much Observed as the holy day began, eating unleavened cakes and parched corn from the already harvested Canaanite crops. During the daylight portion of the holy day, they ate of the same provisions that supplied their meal the previous evening because no manna fell on that Sabbath day. No manna fell the next day, Nisan 16, either.
The notation regarding "old corn" ("produce" in modern versions) is simply given to show where Israel's sustenance came from, since the manna stopped appearing. It is not given to prove that a wavesheaf offering was made because none was required'none could be made in the first place.
John W. Ritenbaugh
Pentecost, Consistency, and Honesty