Jamieson, Fausset and Brown on 2 Chronicles 6:22

22. If a man sin against his neighbour, and an oath be laid upon him to make him swear, and the oath come before thine altar in this house, &c.--In cases where the testimony of witnesses could not be obtained and there was no way of settling a difference or dispute between two people but by accepting the oath of the accused, the practice had gradually crept in and had acquired the force of consuetudinary law, for the party to be brought before the altar, where his oath was taken with all due solemnity, together with the imprecation of a curse to fall upon himself if his disavowal should be found untrue. There is an allusion to such a practice in this passage.