Charles Ellicott Commentary Isaiah 40:10

"Behold, the Lord Jehovah will come as a mighty one, and his arm will rule for him: Behold, his reward is with him, and his recompense before him." — Isaiah 40:10 (ASV)

The Lord God. — Adonai Jehovah; each word commonly translated Lord. The combination is characteristic both of 1 and 2 Isaiah (Isaiah 3:15; Isaiah 28:16; Isaiah 30:15).

With strong hand. — Literally, with, or in strength of hand, as the essence of His being. The “arm” of the Lord is a favourite phrase of Isaiah (Isaiah 51:5; Isaiah 51:9; Isaiah 52:10) for His power.

His reward is with him ... — The noun “work” has also the sense of recompense for the faithful worker (Leviticus 19:13; Deuteronomy 24:15), and is rightly taken in that sense here and in Isaiah 62:11.