Leviticus 5:4
Or if a soul swear, pronouncing with his lips to do evil, or to do good, whatsoever it be that a man shall pronounce with an oath, and it be hid from him; when he knoweth of it, then he shall be guilty in one of these. Or if a soul swear, pronouncing with his lips to do evil, or to do good, whatsoever it be that a man shall pronounce with an oath, and it be hid from him; when he knoweth of it, then he shall be guilty in one of these.
Leviticus 5:4 belongs to the ceremonial law, not the moral law, which was instituted in consequence of sin. It stands among the instructions for individual sins and individual offerings in the first seven chapters of Leviticus, requiring an offering when a transgression became known. A person who became guilty under it was to bring an unblemished animal to the sanctuary, confessing the sin and accepting the animal as a substitute.
The verse makes a person guilty for pronouncing with the lips an oath to do evil or to do good, whatsoever a man shall pronounce with an oath, when it was hid from him and he afterward knows of it. That guilt includes an oath whose implications or wrongness was not recognized when it was made, becoming guilt when what was hidden becomes known. The surrounding law then requires confession of the sin before individual atonement is made for forgiveness.
Sin committed unknowingly is still guilt when it becomes known, so ignorance does not make the sin innocent and does not make a wrong act right. God nevertheless takes account of what a person knew and could have known in judging guilt. Once the matter is known the sin must be confessed, repented of, and put away regardless of good intentions. Confession comes before individual atonement is made for forgiveness, as likewise shown for sins of ignorance in Leviticus 4:22-24 and 27-29.
Without atonement the person bears the iniquity until he presents his offering and slays his own offering. He brings the animal to the sanctuary and the priest uses its blood to make atonement for the sinner, and he is forgiven. The sacrifice figured the transfer of the penitent's sins to the sanctuary through the blood or through the priest, where the forgiven sins were represented as remaining until the yearly service. Bringing such offerings when burdened with sin was to be done in faith as an expression of faith in the Redeemer who was to come.