The topic of the atoning sacrifices’ efficacy has received insufficient treatment in scholarship. Interpreters only sporadically treat this topic, and when they discuss it all, their presentations are far from systematic and largely based on portions of the Bible other than Leviticus. This article remedies this unfortunate gap by examining the efficacy of the atoning sacrifices—the purification (חַטָּאת) and reparation (אָשָׁם) offerings—from the perspective of the Pentateuch, focusing especially on the book of Leviticus. It shows that the atoning sacrifices effect atonement and remove sin and cultic impurity for all nondefiant, but not defiant, offenses. It demonstrates, furthermore, that the atoning sacrifices ultimately find their efficacy in God but do not work ex opere operato in that the book of Leviticus presumes the offerer’s sincerity and penitence. Thus, the atoning sacrifices can be described sacramentally: they function as external rituals by which God seals a promised efficacy regarding atonement, forgiveness, and cleansing.