Isaiah 21:6 - Joseph Benson’s Commentary on the Old and New Testaments

For thus hath the Lord said unto me I speak only what God hath caused me to see and hear in a vision, the particulars whereof are related in the following verses. “The Holy Spirit, to make Isaiah, and, by him, the church, most certain of this memorable event, confirms the preceding revelation by an elegant emblem, offered to the prophet in vision. This emblem exhibits to us the prophet commanded by God to set a watchman, in this verse; and, in what follows, the consequence of the execution of the command, namely, that the watchman attended accurately to the least motion of the nations against Babylon, and, after long expectation, had discovered” what is afterward related. See Vitringa. The reader will observe, that as the command to set a watchman was given to the prophet in a vision, so it was executed by him only in a vision. It signified, however, what should really be done afterward, namely, when the Medes and Persians should march to besiege and attack Babylon.