This is one of the best things William Barclay wrote in his Daily Study Bible:
THE WAITING HARVEST (Matthew 9:37-38)
9:37-38 Then he said to his disciples, “The harvest is great, but the workers are few. Therefore, pray to the Lord of the harvest to send out workers for his harvest.”
Here is one of the most characteristic things Jesus ever said. When he and the orthodox religious leaders of his day looked on the crowd of ordinary men and women, they saw them in quite different ways. The Pharisees saw the common people as chaff to be destroyed and burned up; Jesus saw them as a harvest to be reaped and to be saved. The Pharisees in their pride looked for the destruction of sinners; Jesus in love died for the salvation of sinners.
But here also is one of the great Christian truths and one of the supreme Christian challenges. That harvest will never be reaped unless there are reapers to reap it. It is one of the blazing truths of Christian faith and life that Jesus Christ needs men. When he was upon this earth, his voice could reach so few. He was never outside Palestine, and there was a world which was waiting. He still wants men to hear the good news of the gospel, but they will never hear unless other men will tell them. He wants all men to hear the good news; but they will never hear it unless there are those who are prepared to cross the seas and the mountains and bring the good news to them.
Nor is prayer enough. A man might say, “I will pray for the coming of Christ’s Kingdom every day in life.” But in this, as in so many things, prayer without works is dead. Martin Luther had a friend who felt about the Christian faith as he did. The friend was also a monk. They came to an agreement. Luther would go down into the dust and heat of the battle for the Reformation in the world; the friend would stay in the monastery and uphold Luther’s hands in prayer. So they began that way. Then, one night, the friend had a dream. He saw a vast field of corn as big as the world; and one solitary man was seeking to reap it–an impossible and a heartbreaking task. Then he caught a glimpse of the reaper’s face; and the reaper was Martin Luther; and Luther’s friend saw the truth in a flash. “I must leave my prayers,” he said, “and get to work.” And so he left his pious solitude, and went down to the world to labour in the harvest.
It is the dream of Christ that every man should be a missionary and a reaper. There are those who cannot do other than pray, for life has laid them helpless, and their prayers are indeed the strength of the labourers. But that is not the way for most of us, for those of us who have strength of body and health of mind. Not even the giving of our money is enough. If the harvest of men is ever to be reaped, then every one of us must be a reaper, for there is someone whom each one of us could–and must–bring to God.