Commentary for Exodus 12:5

תמים PERFECT i. e. without blemish (Mekhilta d'Rabbi Yishmael 13:5:1).

ומן העזים תקחו, "or you may take it from amongst the he-goats." The reason the Torah had to write the word תקחו, you shall purchase or take once more is to teach that it is permitted to use a goat even if one owns a sheep of the appropriate age group.

שה תמים, ”an unblemished lamb.” It was appropriate to select a lamb for that sacrifice as the horoscope of the lamb is in its ascendancy during the month of “Nissan.” Consuming the lamb was a reminder to every Israelite that this Egyptian deity had been completely powerless to protect its worshippers. By doing this we testify that our departure from Egypt was not due to our own efforts or ability, but exclusively to the power of Hashem.