John Gill's Exposition of the Whole Bible
Isaiah 51:12
I, even I, am he that comforteth you,.... This is an answer to the prayer of the prophet, or the church by him, in which the Lord promises not only assistance and help, but comfort; not only to exert his power and show his great strength by making bare his arm; but to open his heart, unbosom himself, and show his great love and strong affection for them; and so administer divine comforts unto them, giving more than was asked for: and he promises to do it himself, not by his prophets and ministers, word and ordinances, though these are the usual means; but he himself would do it by his Spirit and grace, and the immediate discoveries of his love; and which he repeats, to show the certainty of it, as well as to point out to their view the great Comforter himself; which is an instance of amazing condescension, and could not fail of exciting admiration and thankfulness in them; see 2 Corinthians 1:3,
who art thou, that thou shouldest be afraid of a man that shall die; a poor faint hearted creature indeed, to be afraid of a frail mortal dying man; which is the case of every man, even of the greatest of men, of the kings and princes of the earth, who all die like other men; the most proud and haughty tyrants, the fierce and furious persecutors of the people of God. Perhaps the Roman Pagan persecutors may be had in view, whose edicts were very terrible to the first Christians, whose persecutions were very violent and furious, and the tortures and deaths they put them to were very dreadful; and which put them in great fear though they had no reason to fear them that could destroy the body, and do no more; and the rather, since these were mortal men, and did die, and their persecutions came to an end. Or it may be, the man of sin, the son of perdition, antichrist, is here referred to, who in his time has made all to tremble at him, Revelation 13:3 but must die, and his power too, and will be destroyed with the breath of Christ's mouth, and the brightness of his coming; and therefore his church and people have no reason to be afraid of him:
and of the son of man, which shall be made as grass; as weak as that, which cannot stand before the scythe, is cut down, and tossed about, and trampled upon, and made hay of, and becomes the food of beasts,
Psalms 90:5. Or the words may be rendered, "and of the son of man, to whom grass shall be given"; r which if understood of Nebuchadnezzar king of Babylon, of whom the people of the Jews were afraid, and who was a type of antichrist, it was literally true of him, Daniel 4:32.
r חציר ינין "herba dabitur", Pagninus, Montanus.