Charles Ellicott Commentary Isaiah 49:4

"But I said, I have labored in vain, I have spent my strength for nought and vanity; yet surely the justice [due] to me is with Jehovah, and my recompense with my God." — Isaiah 49:4 (ASV)

Then I said.—The accents of disappointment sound strangely coming from the lips of the true Servant; but the prophet had learned by his own experience that this formed part of the discipline of every true servant of God, in proportion to the thoroughness of his service, and therefore it was not strange to him that the ideal Servant should also taste that bitterness. We find in the prophet of Anathoth a partial illustration of the law (Jeremiah 20:14). We find its highest fulfillment in the cries of Gethsemane and Golgotha. The sense of failure is surmounted only, as here, by looking to a judgment other than man’s, and another reward (better than “work”). (Compare to 1 Corinthians 4:3.)