He spake unto them in the cloudy pillar That is, to some of them: to Moses frequently, and to Aaron sometimes, as Numbers 12:5. And although it is not anywhere expressly said that God spake unto Samuel out of the cloudy pillar, yet, as Dr. Hammond observes, it is probable enough from his history that he did so; for when Samuel was so signally heard by God at Mizpeh, 1 Samuel 7., it is said, 1 Samuel 7:9, The Lord answered him; and 1 Samuel 7:10, The Lord thundered with a great thunder, which supposes a cloud, if not a cloudy pillar; and so this answering of Samuel with thunder, must be God's speaking to him at this time out of the cloud. They kept his testimonies This is added, not only for their commendation, but for the instruction of the Israelites, to teach them that God would not hear the prayers of them who did 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.