Isaiah
Isaiah 51:12ESV·traditional attribution

“I, I am he who comforts you; who are you that you are afraid of man who dies, of the son of man who is made like grass,

Matthew Henry Presbyterian @wholebiblehenry

In these verses we have, I. A prayer that God would, in his providence, appear and act for the deliverance of his people and the mortification of his and their enemies. Awake, awake! put on strength, O arm of the Lord! Isa 51:9. The arm of the Lord is Christ, or it is put for God himself, as Psa 44:23. Awake! why sleepest thou?

Commenting on Isaiah 51:9-16

John Gill Reformed Baptist @doctorgill

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...

Jamieson-Fausset-Brown Reformed @jfbcommentary

comforteth-- (Isa 51:3; Isa 40:1). thou--Zion. son of man--frail and dying as his parent Adam. be made as grass--wither as grass (Isa 40:6-7).