Unto them, i.e. to some of them; for the expression is only indefinite, and therefore doth not necessarily reach to all of them: to Moses frequently; to Aaron, Exodus 19:24, Exodus 33:9-11 Numbers 12:5; and for Samuel, he answered him, if not by words, yet really and by his actions, thundering against the Philistines, 1 Samuel 7:9, &c, which supposeth a cloud, if not a cloudy pillar. They kept his testimonies, and the ordinance that he gave them: this is added, not only for their commendation, but for the instruction of the Israelites, to teach them that God will not hear the prayers of them who do not keep his commandments.
Related Commentaries of Psalms 99:7
Psalms 99:7
7 He spake unto them in the cloudy pillar: they kept his testimonies, and the ordinance that he gave them.