The sin offering.
Archimandrite Nikifor’s Biblical Encyclopedia
Belonging to the category of propitiatory sacrifices, this offering and the trespass offering were closely connected with one another, though they formed two distinct kinds of sacrifice. The sin offering differed according to the person for whom it was offered and according to the degree of sinfulness that was to be atoned for. Thus, for example, a young bull was prescribed as the sin offering at the consecration of the priests and Levites (Exod. 29:10; Num. 8:7–12), for the high priest on the great Day of Atonement (Lev. 16:3 [as given]; 4:18, 19), when the high priest had sinned to the scandal of the people (Lev. 4:3–12), or when the whole congregation had sinned (Lev. 4:13, 21); a male goat was offered at the new moons and yearly feasts for the sins of the people (Num. 28:22, 30), at the dedication of the tabernacle and of the temple (Num. 7:16, 22; Ezra 6:17); a female goat or a female lamb for the transgressions of any one of the people, for a sin committed in error (Lev. 4:27, 28, 32); a lamb of the first year and a ewe lamb of the first year at the release of the vow of the Nazirites (Num. 6:14, 16, 19) and at the cleansing of a leper (Lev. 14:10, 19); a turtledove or young pigeon at the purification of a woman after childbirth (Lev. 12:6), of a woman who had suffered a long issue of blood (Lev. 15:29, and elsewhere), and in place of a lamb, for the poor, in cases of ordinary sin (Lev. 5:7); wheat flour, a tenth part of an ephah without oil or frankincense, for an ordinary sin, for one who was utterly poor and could not afford to offer even a pigeon.