Without blemish. — Natural piety teaches that we must not “offer the blind, the lame, or the sick for sacrifice” (Malachi 1:8). We must give to (God of our best. The Law emphasized this teaching, and here, on the first occasion when a sacrifice was formally appointed, required it to be absolutely without blemish of any kind. Afterwards the requirement was made general (Leviticus 22:19-25). It was peculiarly fitting that the Paschal offering should be without defect of any kind, as especially typifying “the Lamb of God,” who is “holy, harmless, undefiled” — a “lamb without spot.”
A male. — Males were reckoned superior to females, and were especially appropriate here, since the victim represented the firstborn male in each house.
Of the first year — i.e., not above a year old. As children are most innocent when young, so even animals were thought to be.