Midrash Shmuel 4:1

Once Rabbi Ishmael and Rabbi Akiva were strolling in the streets of Jerusalem along with another man. They met a sick person who said to them, “Masters, can you tell me how I can be healed?” They said to him, "Take such-and-such until you felt better." The man strolling with the two rabbis turned to them and said, “Who made this man sick?” “The Holy Blessed One,” they replied. “And you presume to interfere in an area that is not yours?” the man remarked. “God has afflicted and you heal?” “What is your occupation?” they asked the man. “I’m a tiller of the soil,” he answered, “as you can see from the sickle I carry.” “Who created the land and who created the vineyard?” “The Holy Blessed One.” And they said, “And you dare to move into an area that is not yours? God created these and you eat their fruit?” He said to them, “Don’t you see the sickle in my hand?” the man asked. “If I did not go out and plow the field, water it, fertilize it, weed it, no food would grow!” Fool,” the rabbis said, “have you not heard that the days of people are like a harvest. Just as a tree that is not fertilized and weeded and pruned does not grow, and if it grows and does not drink (or take fertilizer) it does not live and dies, so to the body is a tree—the medicine is the fertilizer and the doctor is the farmer.” [AJWS translation]