What does John 4:36 mean?

The physical and emotional payoff of planting crops comes when those returns are finally harvested. This is a time of happiness for everyone involved. And yet, the primary joy is for those who do the reaping: those bringing in the finished goods. Spiritually, those who plant seeds of the gospel are not always the same people who see those seeds take root and grow. Most often, people come to faith in Christ after one person plants a seed, a different person nourishes it, and still another helps the person express truly saving faith (1 Corinthians 3:5–9).

Earlier, the Samaritan woman mentioned the Messiah (John 4:25). She also mentions Messiah to the people in town after speaking with Jesus (John 4:29). It's possible that she'd heard these ideas from the followers of John the Baptist. In other words, seeds have been planted in this area—the disciples need to pay attention and see where there are opportunities for a harvest! Jesus' earlier remark (John 4:35) suggests this very idea. Others have planted seeds, now the time has come to bring those returns in.