Four independent verses say that the time of the exodus was, and the time to keep Passover/Unleavened Bread is, during the month of THE Aviv.
Now the flax and barley were ruined, for the barley was in the ear (אָבִ֔יב) and the flax was in bud; but the wheat and the emmer were not hurt, for they ripen late.
You go free on this day, in the month of the Aviv (הָאָבִֽיב).
You shall observe the Feast of Unleavened Bread — eating unleavened bread for seven days as I have commanded you — at the set time in the month of the Aviv (הָֽאָבִ֔יב), for in it you went forth from Egypt; and none shall appear before Me empty-handed
You shall observe the Feast of Unleavened Bread — eating unleavened bread for seven days, as I have commanded you — at the set time of the month of the Aviv (הָאָבִ֑יב), for in the month of the Aviv (הָֽאָבִ֔יב) you went forth from Egypt.
Observe the month of the Aviv (הָאָבִ֔יב) and offer a passover sacrifice to the LORD your God, for it was in the month of the Aviv (הָֽאָבִ֗יב), at night, that the LORD your God freed you from Egypt.
The month is not perpetually called Aviv just because that was when they left Egypt. The month is called Aviv because aviv barley literally defines the month. This means that the barley must be AVIV for it to be the month of THE AVIV – you can’t call the month AVIV if the barley is not AVIV.
If we had a Temple service today – this would be abundantly apparent. There is a short window of time in which the barley is in the correct stage for the omer offering during the week of Unleavened Bread. If the barley is not in the right stage, we would not be able to fulfill the commandment and bring the offering during the Feast of Unleavened Bread. To read more about the barley harvest and offering please visit The Temple Institute.
Exodus 9 says that the time of THE AVIV is the time the barley was budding. Brown Driver Briggs’s includes barley in the definition of Aviv (abib):
H24 – אביב
1) fresh, young barley ears, barley
2) month of ear-forming, of greening of crop, of growing green Abib, month of exodus and passover (March or April)
The stages of barley ripening, and the rate at which it ripens, are a direct sign of more light and heat from the sun that brings on spring. Barley being in the “aviv” stage is a visible way for us to determine that spring has truly arrived.
If you want to know more about what the aviv stage is, and how it is determined, I recommend the podcast at this link.