John 6:28 Then they said to Him, “What shall we do, that we may work the works of God?” 29 Jesus answered and said to them, “This is the work of God, that you believe in Him whom He sent.”
John 6:22 - 59
ESV - 22 On the next day the crowd that remained on the other side of the sea saw that there had been only one boat there, and that Jesus had not entered the boat with his disciples, but that his disciples had gone away alone. 23 Other boats from Tiberias came near the place where they had eaten the bread after the Lord had given thanks.
For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
I hope I was clear in my answer to this very important question. Believing in Jesus is the result of God's work. Again, believing is the result, not the labor. Believing is the harvest, not the seed. The gospel is the seed. Scattering the seed is the labor, the work. Who scatters the seed?
Matthew 13 tells the parable of the sower. Beginning in vs 18, Jesus explains the parable to them, but He doesn't say who the sower is. The emphasis is on the soil and the seed, not the sower.
Then He tells them another parable, the parable of the weeds (Matthew 13:24-30). In this one, the sower is a little clearer. The servants of the landowner brings it to the owners attention that his field has weeds growing in it. They question him about the seed he used. He says 'the weeds were planted by an enemy of his.'
Here it is: the landowner was called master by the servants. The landowner only supplies the seed, he doesn't go out to the field and plant, he sends out his workers. They said to him 'Master, did you not sow good seed in your field?'
It's God's seed and it's God's work. The servants are God's servants. The harvest is God's harvest. Jesus said 'As the Father sent Me, so I am sending you' (John 20:21).
It is the work of the sower to scatter seed. Some of it will fall on rocks and thorns. Some of it will fall on ground that the landowner prepared to receive the seed. If he had removed the rocks and thorns the soil would produce a harvest. It's up to him not the soil.