Jesus wanted His disciples to see that the time for gathering people into God's kingdom had already come. They were thinking about food (John 4:31-33), and Jesus had just told them His meat was "to do the will of him that sent me, and to finish his work" (John 4:34). Barnes thinks the saying "seems to have been a proverb," and he notes that the common time in Judea from sowing to harvest was about four months. Jesus used that familiar wait as a contrast. Gill says Christ was speaking "spiritually, of a harvest of souls," and he takes the Samaritans then coming out of the city as the souls Jesus called the disciples to behold, suggesting to them "it was not a time for eating and drinking, but for working."

Jesus answers His own question at once: "behold, I say unto you, Lift up your eyes, and look on the fields; for they are white already to harvest" (John 4:35). He adds that "he that reapeth receiveth wages, and gathereth fruit unto life eternal," and that the disciples were sent to reap where "other men laboured" (John 4:36-38). The harvest followed: "many of the Samaritans of that city believed on him" because of the woman's word, and "many more believed because of his own word" (John 4:39-41). They confessed Him as "the Christ, the Saviour of the world" (John 4:42).

Farmers in Judea expected a wait between sowing and reaping. Barnes says the common time from sowing the seed to the harvest there was about four months. The Greek word for "four months" is tetramēnos, a single word meaning a four-month span. When Jesus says the fields are "white," He uses the language of ripe grain. Barnes explains: "Grain, when ripe, turns from a green to a yellow or light color, indicating that it is time to reap it."

The Samaritans were a people the Jews avoided; the woman herself said, "the Jews have no dealings with the Samaritans" (John 4:9). That makes the readiness of this Samaritan town all the more surprising.

This question shows that God's work often runs ahead of our expectations. The disciples saw a Samaritan town and an ordinary season. Jesus saw people ready to believe. Matthew Henry writes that "gospel time is harvest time, and gospel work harvest work."

Jesus also places the disciples in a longer story. Others had sown before them (John 4:37-38). Barnes names the prophets, the teachers among the Jews, John the Baptist, and the Saviour Himself as those who labored first, and he notes that the work of sower and reaper alike depends on God giving the increase. The harvest belongs to God, and sower and reaper "may rejoice together" (John 4:36).