"Then Jesus went about all the cities and villages, teaching in their synagogues, preaching the gospel of the kingdom, and healing every sickness and every disease among the people. But when He saw the multitudes, He was moved with compassion for them, because they were like sheep having no shepherd. Then He said to His disciples, 'The harvest truly is plentiful, but the laborers are few. Therefore pray the Lord of the harvest to send out laborers into His harvest. And when He had called His twelve disciples to Him, He gave them power over unclean spirits, to cast them out, and to heal all kinds of sickness and all kinds of disease" (Matt. 9:35-10:1).
Matthew 9:35 provides a good summary of Jesus' work during His earthly ministry. He both preached and healed extensively. There never was a physical sickness or disease that Jesus could not cure. Jesus was "moved with compassion for them [the multitudes], because they were weary and scattered, like sheep having no shepherd." Jesus, the good shepherd (John 10:11), came to gather the fold and give them rest (Matt. 11:28). He genuinely cared for people, and His compassion moved Him to action.
He instructed His disciples - "The harvest truly is plentiful, but the laborers are few." The world at that time was comparable to a harvest because many were ripe for knowledge, ready to hear, and ready to become His disciples. The only thing lacking was teachers. Thus, they were told to "pray the Lord of the harvest to send out laborers into His harvest." One cannot sincerely offer this prayer without realizing his own responsibility to labor in the Lord's harvest.
As Matthew 10 begins, Jesus made these men capable of doing what He wanted them to do--preach! They needed the power to work miracles in order to gain the attention, respect, and confidence of the people. The power He supplied them would enable them to teach effectively. Let all understand that God never expects more of His followers than they are capable of giving (cf. II Cor. 8:12). He knows the limits of each one and will always provide His servants with the means to accomplish His will.
Matthew 10:5-8 records - "These twelve Jesus sent out and commanded them, saying: 'Do not go into the way of the Gentiles, and do not enter a city of the Samaritans. But go rather to the lost sheep of the house of Israel. And as you go, preach, saying, "The kingdom of heaven is at hand." Heal the sick, cleanse the lepers, raise the dead, cast out demons. Freely you have received, freely give.'"
Mark mentions that He sent them out in pairs (6:7), but more important is the simple fact that He sent them out. His compassion was not merely an emotion and His prayers were not without action. May His disciples today not be content with prayer without action, and may compassion always motivate genuine efforts to help.
Although Jesus' disciples did not always travel in pairs (e.g., Acts 8:5ff), they generally did, and for at least three good reasons: (1) They could supplement each other's work (certain men are more effective at reaching certain individuals, and where one fails another may succeed), (2) They would be a great source of encouragement to each other (when one became discouraged the zeal and enthusiasm of the other would help cheer him up and keep him motivated and focused), and (3) They would be much safer traveling in pairs rather than alone.
Jesus first tells them explicitly where not to go - "Do not go into the way of the Gentiles, and do not enter a city of the Samaritans" (Matt. 10:5). He then proceeds to tell them where to go - "Go rather to the lost sheep of the house of Israel." Jesus Himself, during His earthly ministry, was sent only to the Jews. The rationale for this is based on the fact that the Jews should have been better prepared to receive the Messiah than any Gentiles. After all, they had the Law, the Prophets, and the preparatory work of John the baptizer. The time for the Gentiles to hear the gospel would come later (cf. Rom. 1:16). In fact, after Jesus' resurrection, this "limited commission" (as it is often called) would be expanded (cf. Matt. 28:18-20; Mark 16:15,16) though the application of this expansion would not be realized until years later (cf. Acts 10).
As they went, Jesus expected them to preach - "The kingdom of heaven is at hand." Their central theme was the same as that which John had introduced and Jesus had already been proclaiming (cf. Matt. 3:2,17). At that time the kingdom wasn't established yet though it wouldn't be long until its beginning on the Day of Pentecost in Acts 2.
They were also instructed - "Freely you have received, freely give." They were not to sell miracles or to accept bribes, though they certainly could have become rich in so doing. To charge for these works would have shown the motive to be greed and not compassion. It also would have robbed the power of its dignity by turning it into a service that could be bought and sold like common merchandise.