This month [Abib/Nisson] is to be the beginning of months for the congregation of Israel. It is the first month of your year.
Tell the whole community of Israel that on the tenth day of this month they must each select an animal of the flock, according to their fathers households, one animal per household.
You are to keep it until the fourteenth day of this month, then the whole assembly of the congregation of Israel will slaughter the animals at twilight. Let nothing of it remain until the morning. That which remains of it until morning you shall burn with fire. Exodus 12:2,3,6,10