I sent you to reap that whereon ye bestowed no labour: other men laboured, and ye are entered into their labours.
John 4:38 (KJV)
Jesus says that reaping requires labor, or, effort. There are apparently different kinds of effort.
Jesus is using farming as a symbol for spiritual effort. Reaping a harvest takes great effort. It may take more effort than any part of the crop producing process.
However, you can’t even have a harvest to reap unless there is the effort of planting the seed and tending the crops. This will always precede bringing in the harvest.