Exodus 12:5 - Joseph Benson’s Commentary on the Old and New Testaments

Your lamb shall be without blemish Shall be perfect, as the Hebrew is, that is, in all its parts. This was a qualification indispensably requisite in all sacrifices: Leviticus 22:20-24. Even the heathen, in the worship of their false gods, were particular in this circumstance. A male Because the males were accounted more excellent, and their flesh better than that of females. Of the first year Under a year old, not above: for the lamb, as also a kid and calf, was fit for sacrifice at eight days old, but not before, Exodus 22:30. And the same law was observed in the daily sacrifice, Exodus 29:38. They were not to be offered before the eighth day, “because,” says Bochart, “till then they have hardly attained to the perfection of animal life, and are not sufficiently purified.” He adds, “they were not to be offered after the first year, because then they begin to feel the heat of libidinous appetite, and consequently are not fit emblems of purity and innocence.”