I saw in the visions of my head upon my bed, and, behold, a watcher and an holy one came down from heaven;
I saw ... a watcher and an holy one came down from heaven - rather, 'even an holy one.' Only one angel is intended, and he not one of the bad, but of the holy angels. Called a "watcher," because ever on the watch to execute God's will (Jerome). (Psalms 103:20-21.) Compare as to the watchfulness of 'the four living creatures' (so the Greek) or cherubim (Revelation 4:8, "full of eyes within ... they rest not day and night"). Also they watch good men committed to their charge (Psalms 34:7; Hebrews 1:14); and watch over the evil, to record their sins, and at God's bidding at last to punish them (Jeremiah 4:16-17, "watchers," applied to human instruments of God's vengeance). As to GOD (Daniel 9:14; Job 7:12; Job 14:16; Jeremiah 44:27). In a good sense (Genesis 31:49; Jeremiah 31:28).
The idea of heavenly "watchers" under the supreme God (called in the Zendavesta of the Persian Zoroaster, 'Ormuzd') was founded on the primeval revelation as to evil angels having watched for an opportunity until they succeeded in tempting man to his ruin, and good angels ministering to God's servants (as they did to Jacob, Genesis 28:15; Genesis 32:1-2, "Jacob went on his way, and the angels of God met him. And when Jacob saw them, he said, This is God's host: and he called the name of that place Mahanaim" - that is, two hosts). Compare the watching over Abraham for good, and over Sodom for wrath, after long watching in vain for good men in it, for whose sake he would spare it, Genesis 18:1-33: and over Lot for good, Genesis 19:1-38. Daniel fitly puts in Nebuchadnezzar's mouth the expression, though not found elsewhere in Scripture, yet substantially sanctioned by it (2 Chronicles 16:9; Proverbs 15:3; Jeremiah 32:19), and natural to him, according to Oriental modes of thought.