If you be prophets, as you pretend, yet know there is a difference among prophets, nor do I put equal authority and honour upon all of them. By a vision God represents things to the mind of a prophet when he is awake, as Genesis 15:1, Genesis 46:2 Daniel 8:18, Daniel 10:8. By a dream God manifests his mind to them when asleep, as Genesis 20:3, Genesis 28:12.
Related Commentaries of Numbers 12:6
Numbers 12:6
6 And he said, Hear now my words: If there be a prophet among you, I the LORD will make myself known unto him in a vision, and will speak unto him in a dream.