And the voice which I heard from heaven,.... In Rev 10:4; spake to me again, and said, go and take the little book which is open in the hand of the angel which standeth upon the sea and upon the earth; as John was to prophesy, Rev 10:11; it was necessary that he should have a mission and a commission from heaven; and that he should have the open book of prophecy to prophesy out of; and that he should receive this from the angel's hands, who had unloosed its seals, and opened it: and just so to ordinary prophesying, or preaching, it is necessary that men should have their commission from heaven, should be called of God, and sent by him; and that they should have the book of the Scriptures before them, and open to them, and speak according to these oracles, agreeably to the law and to the testimony, which are profitable for doctrine; and that they should also receive the Gospel, and the doctrines of it, with gifts, and a commission to preach it, from the Angel of the covenant, Jesus Christ, who has all power both in heaven and in earth; see Rev 10:2.