The harvest is indeed abundant By this metaphor he intimates, that many of the people are ripe for receiving the gospel. Though the greater number afterwards rejected basely and with vile ingratitude the salvation offered to them, yet the limited number of the elect, who were mixed with unbelievers, is compared to an abundant harvest, because God values a small band of his own people more highly than the rest of the world. Though there were at that time many who assumed this character, yet as few of them discharged it faithfully, he does not rank them among laborers: for he employs the word laborers in a good sense. When Paul complains (2-Corinthians 2:13) of bad laborers, he refers to their boasting: for he would not have bestowed the designation of laborers [1] on those who devoted all their exertions to ruin and waste the flock, had it not been that they gloried in the false pretense.

Footnotes

1 - ergatai dolioi, deceitful workmen.

The harvest truly is plenteous - Another beautiful image. A waving field of golden grain invites many reapers and demands haste. By the reference to the harvest here, he meant that the multitude of people that flocked to his ministry was great. The people expected the Messiah. They were prepared to receive the gospel; but the laborers were few. He directed them, therefore, to pray to the Lord of the harvest to send forth reapers. God is the proprietor of the great harvest of the world, and he only can send people to gather it in.
Remarks On Matthew 9
1. We are presented with an instance of proper perseverance in coming to Christ, Matthew 9:1-2. Nothing was suffered to prevent the purpose of presenting the helpless paralytic to the Saviour. So the poor helpless sinner should come. No obstacle should prevent him. He should lay himself at his feet, and feel that Jesus holds over him the power of life and death, and that no other being can save.
2. Jesus has the power to forgive sins, Matthew 9:6. He claimed it, and worked a miracle to prove it. If he had it then, he has it still. To him, then, the lost sinner may come with the assurance that as he freely "then" exerted that power, so he is ever the same, and will do it now.
3. Jesus Christ is divine. Nothing could prove it more clearly than the power to pardon sinners. Only God can pronounce what shall be done with transgressors of His law, Isaiah 43:25. He that claims this right must be either an impostor or God. But no impostor ever yet worked a real miracle. Jesus was therefore divine. He can save to the uttermost all who come to God through him.
4. We see here the proper rule to be observed in mingling with the wicked, Matthew 9:10-13. It should not be of choice or for pleasure. We should not enter into their follies or vices. We should not seek enjoyment in their society. We should mingle with them simply to transact necessary business and to do them good, and no further, Psalm 1:1.
5. In the case of the ruler and the woman that was diseased, we have a strong instance of the nature of faith. They came not doubting the power of Jesus - fully assured that he was able to heal. So all genuine believers come to him. They do not doubt his power or willingness to save them. Poor, and lost, and ruined by sin, and in danger of eternal death, they come. His heart is open. He puts forth his power, and the soul is healed, and the sin and danger gone.
6. The young must die, and may die in early life, Matthew 9:18. Very short graves are in every burying-ground. Thousands and millions, not more than twelve years of age, have died. Thousands and millions, not more than twelve years of age, are yet to die. Many of these may be taken from Sunday schools. Their class, their teacher - their parents, sisters, brothers - must be left, and the child be carried to the grave. Many children of that age that have been in Sunday schools have died happy. They loved the Saviour, and they were ready to go to him. Jesus was near to them when they died, and they are now in heaven. Of every child we may ask, Are you ready also to go when God shall call you? Do you love the Lord Jesus, so as to be willing to leave all your friends here and go to him?
7. Jesus can raise up the dead, and he will raise up all that love him, Matthew 9:25. Many little children will be raised up to meet him in the last great day. He shall come in the clouds. The angel shall sound a trumpet, and all the dead shall hear. All shall be raised up and go to meet him. All that loved him here will go to heaven. All who were wicked, and did not love him here, will go to everlasting suffering.
8. We see the duty of praying for the conversion of the world, Matthew 9:37-38. The harvest is as plenteous as it was in the time of Christ. More than 600 million are still without the gospel, and there are not still many laborers to go into the harvest. The world is full of wickedness, and only God can qualify those who shall go and preach the gospel to the dark nations of the earth. Without ceasing we ought to entreat of God to pity the nations, and to send to them faithful people who shall tell them of a dying Saviour.

The harvest - The souls who are ready to receive the truth are very numerous; but the laborers are few. There are multitudes of scribes, Pharisees, and priests, of reverend and right reverend men; but there are few that work. Jesus wishes for laborers, not gentlemen, who are either idle drones, or slaves to pleasure and sin, and nati consumere fruges. "Born to consume the produce of the soil."
It was customary with the Jews to call their rabbins and students reapers; and their work of instruction, the harvest. So in Idra Rabba, s. 2. "The days are few; the creditor is urgent; the crier calls out incessantly; and the reapers are few." And in Pirkey Aboth: "The day is short, the work great, the workmen idle, the reward abundant, and the master of the household is urgent." In all worldly concerns, if there be the prospect of much gain, most men are willing enough to labor; but if it be to save their own souls, or the souls of others, what indolence, backwardness, and carelessness! While their adversary, the devil, is going about as a roaring lion, seeking whom he may devour; and a careless soul, and especially a careless minister is his especial prey.
The place of the harvest is the whole earth: it signifies little where a man works, provided it be by the appointment, in the Spirit, and with the blessing of God.

Then saith he unto his disciples,.... His heart being drawn out, and filled with pity to these poor people, upon observing the miserable and sad condition they were in; he turns himself to his disciples, whom he was about to call, and send forth in a more public manner to preach the Gospel, of which we read in the following chapter; and in order to quicken them to this service, and engage their hearts in it, says unto them,
the harvest truly is plenteous; meaning the large number of God's elect, which were in these cities, towns, and villages, and in other places: not that these were maturely prepared by anything in themselves, or done by them, for the grace of God; and much less ripe for the kingdom of glory, and therefore called an harvest: but as there are the appointed weeks of the harvest, or a set time for the harvest to be gathered in, so there is a certain fixed time, settled in the counsel, and by the purpose of God, for the effectual calling and conversion of his elect; and this time being come, with respect to these in Galilee, and other parts, Christ calls them an "harvest"; and because of their number, a large, or "plenteous" one.
But the labourers are few: Gospel ministers; whose calling is a laborious one; whose business is to labour in the word and doctrine; to be constant in prayer; to give up themselves to meditation and reading; to study to show themselves workmen; to preach the word in season, and out of season; and diligently discharge the several duties of their office, to the glory of Christ, and the good of souls: but such painful and laborious ministers, who are willing to spend, and be spent for Christ and immortal souls, have been but few in all ages; generally speaking, there are more loiterers than labourers.

Then saith he unto his disciples, The harvest truly is plenteous--His eye doubtless rested immediately on the Jewish field, but this he saw widening into the vast field of "the world" (Matthew 13:38), teeming with souls having to be gathered to Him.
but the labourers--men divinely qualified and called to gather them in.

The harvest truly is plenteous, but the laborers are few. First the people are represented under the figure of sheep, scattering abroad, without a shepherd's care; next as a ripe and abandoned harvest, ready to be lost unless reapers are sent to gather it.

The harvest truly is great - When Christ came into the world, it was properly the time of harvest; till then it was the seed time only. But the labourers are few - Those whom God sends; who are holy, and convert sinners. Of others there are many. Luke 10:2.