Rashi on Exodus 12:5/רש"י על שמות י״ב:ה׳

1תמים PERFECT i. e. without blemish (Mekhilta).

2בן שנה OF THE FIRST YEAR — the whole of its first year it is termed שנה בן, as much as to say, that it was born during this year (it does not mean that it is one year old — in its second year) (cf.Mekhilta).

3מן הכבשים ומן העזים — i. e. either from these (a lamb) or from these (a goat) (i. e. the ו of ומן does not signify “and”, but “or”); for a goat, also, is called שה, as it is said, (Deuteronomy 14:4) “the שה of the goats” (שה means the young animal, either of the sheep or of the goats) (cf. Mekhilta).