Albert Barnes Commentary Leviticus 4:23

"if his sin, wherein he hath sinned, be made known to him, he shall bring for his oblation a goat, a male without blemish." — Leviticus 4:23 (ASV)

Or if his sin - Rather, And if his sin.

Come to his knowledge - That is, when he had become conscious of his sin.

A kid of the goats - A shaggy he-goat, in distinction from a smooth-haired he-goat. It was the regular sin-offering at the yearly festivals (Leviticus 16:9), (Leviticus 16:15); (Numbers 28:15), (Numbers 28:22), (Numbers 28:30), and at the consecration of the priests (Leviticus 9:3); while the smooth-haired goat appears to have been generally offered for the other sacrifices (Psalms 50:9); (Isaiah 1:11).