Numbers 16:5

and he spake unto Korah and unto all his company, saying, Even to-morrow the Lord will show who are His and who is holy, the reference being to the priestly office, for which Aaron had been consecrated by the special command of the Lord; and will cause him to come near unto Him, even him whom He hath chosen will He cause to come near unto Him. God Himself would indicate whom He had selected to offer the sacrifices before Him in the Sanctuary. Moses was willing to submit the entire matter to a test.