John Calvin on John 4:34

34. My food is to do the will of him who sent me. He means not only that he esteems it very highly, but that there is nothing in which he takes greater delight, or in which he is more cheerfully or more eagerly employed; as David, in order to magnify the Law of God, says not only that he values it highly, but that it is sweeter than honey, (Psalm 19:10.) If, therefore, we would follow Christ, it is proper not only that we devote ourselves diligently to the service of God, but that we be so cheerful in complying with its injunctions that the labor shall not be at all oppressive or disagreeable.

That I may finish his work. By adding these words, Christ fully explains what is that will of the Father to which he is devoted; namely, to fulfill the commission which had been given to him. Thus every man ought to consider his own calling, that he may not consider as done to God what he has rashly undertaken at his own suggestion. What was the office of Christ is well known. It was to advance the kingdom of God, to restore to life lost souls, to spread the light of the Gospel, and, in short, to bring salvation to the world. The excellence of these things caused him, when fatigued and hungry, to forget meat and drink. Yet we derive from this no ordinary consolation, when we learn that Christ was so anxious about the salvation of men, that it gave him the highest delight to procure it; for we cannot doubt that he is now actuated by similar feelings towards us.

John 4:35-38

35. Do you not say, There are yet four months, and harvest will come? Lo, I say to you, Lift up your eyes, and look at the fields, for they are already white for harvest. 36. And he who reapeth receiveth reward, and gathereth fruit into life eternal; that both he that soweth, and he that reapeth, may rejoice together. 37. For in this is the saying true, That there is one who soweth, and another who reapeth. 38. I sent you to reap that on which you did not labor; other men labored, and you have entered into their labors.