Matthew Poole and continuators on Psalms 99:6

6 Moses and Aaron among his priests, and Samuel among them that call upon his name : they called upon the LORD, and he answered them .

He presseth them to perform the duty of praising and worshipping God by the examples of three eminent persons who practised this duty, and that with happy success. He reckoneth Moses among the Priests not without cause, partly because before the institution of the Priesthood he executed that office, Exod. 24. 6. Numb. 7. and partly because he oft interceded to God for the people; which was a very considerable part of the Priests work. See Numb. 6. 23, &c. Ioel 2. 17.

Who used frequently and solemnly to intercede with God on the behalf of the people. So the general expression is here used synecdochically for this particular kind of prayer: such Synecdoche's being very frequent in Scripture.

Moses, Exod. 32. and elsewhere; Aaron, Numb. 16. Samuel, 1 Sam. 7. 19. and 12. 19. Compare Ier. 15. 1.