I definitely see the application of what others have mentioned, but this verse should be taken in unison with what was taking place prior.
Jesus is talking to his disciples about how to deal with people, and more specifically offenses. He tells them how important it is to forgive if asked for forgiveness. (He later makes statements about forgiveness that go beyond someone asking for forgiveness in Matthew 18:21.) But the disciples asked the Lord to increase their faith. and he replies with:
5 The apostles said to the Lord, “Increase our faith!” 6 He replied, “If you have faith as small as a mustard seed, you can say to this mulberry tree, ‘Be uprooted and planted in the sea,’ and it will obey you. 7 “Suppose one of you has a servant plowing or looking after the sheep. Will he say to the servant when he comes in from the field, ‘Come along now and sit down to eat’?
He goes on to the parable about the servant making a comparison to our faith. This verse is specifically talking about how to use your faith. Use your faith whenever you can, and as much as you can find use for it. The role of faith is to serve you! Not the other way around!
I see that people have taken this verse to mean they are supposed to be out serving other people, and I agree that this is something God wants all His children to experience. It keeps Satan off your back, and it releases you from self centered-ness. But I disagree that there isn't a reward for those who serve others, or that that reward is only in Heaven. Why wouldn't you look forward to something God promises. Jesus said prior in Luke 6:
32 “If you love those who love you, what credit is that to you? Even sinners love those who love them. 33 And if you do good to those who are good to you, what credit is that to you? Even sinners do that. 34 And if you lend to those from whom you expect repayment, what credit is that to you? Even sinners lend to sinners, expecting to be repaid in full. 35 But love your enemies, do good to them, and lend to them without expecting to get anything back. Then your reward will be great, and you will be children of the Most High, because he is kind to the ungrateful and wicked. 36 Be merciful, just as your Father is merciful. 37 “Do not judge, and you will not be judged. Do not condemn, and you will not be condemned. Forgive, and you will be forgiven. 38 Give, and it will be given to you. A good measure, pressed down, shaken together and running over, will be poured into your lap. For with the measure you use, it will be measured to you.”
I would follow up with Galatians 4:
4 Now I say that the heir, as long as he is a child, does not differ at all from a slave, though he is master of all, 2 but is under guardians and stewards until the time appointed by the father. 3 Even so we, when we were children, were in bondage under the elements of the world. 4 But when the fullness of the time had come, God sent forth His Son, born[a] of a woman, born under the law, 5 to redeem those who were under the law, that we might receive the adoption as sons.
Forgiveness and service can freely flow as we begin to understand the forgiveness and service God has issued towards us as a free gift. There is a reward in serving others, but without faith it's impossible to please God.
