Jamieson, Fausset and Brown on Leviticus 5:1

CHAPTER 5

Le 5:1. Trespass Offerings for Concealing Knowledge.

1. if a soul ... hear the voice of swearing--or, according to some, "the words of adjuration." A proclamation was issued calling any one who could give information, to come before the court and bear testimony to the guilt of a criminal; and the manner in which witnesses were interrogated in the Jewish courts of justice was not by swearing them directly, but adjuring them by reading the words of an oath: "the voice of swearing." The offense, then, for the expiation of which this law provides, was that of a person who neglected or avoided the opportunity of lodging the information which it was in his power to communicate.

Le 5:2, 3. Touching Any Thing Unclean.