Deuteronomy 33:8

And of Levi he said, Let thy Thummim and thy Urim, Exodus 28:30, the guarantee that the Lord would ever protect the rights of His people by revealing to the priests His holy will and the manner in which they were to comport themselves, be with thy holy one, with the tribe of Levi, from which the high priest was consecrated to the Lord, whom thou didst prove at Massah, and with whom thou didst strive at the waters of Meribah, Exodus 17:1; Numbers 20:1; for although the people, in either instance, murmured against the Lord, yet the Lord made use of both occurrences to test their faith;