Read Matthew 10.
Christ sent the Twelve disciples on a brief preaching mission in this chapter. The first 15 verses describe the call and commission of these Apostles as well as the specific instructions Christ had for this mission.
After verse 16, Jesus described aspects of discipleship that could apply to anyone who witnesses for him. He told the disciples they would be forced to choose either to love family or to love Christ (vv. 34-39).
Not everyone disciples know or meet will reject them. At the end of the chapter Jesus indicated that some will welcome the disciples because they welcome Jesus (v. 40). This alludes to the fellowship that believers have with one another because of our fellowship with Christ.
But Christ went further than just alluding to the fact that some people will receive us. He promised a great reward for those who receive us. Verse 41 says, “Whoever welcomes a prophet as a prophet will receive a prophet’s reward, and whoever welcomes a righteous person as a righteous person will receive a righteous person’s reward. And if anyone gives even a cup of cold water to one of these little ones who is my disciple, truly I tell you, that person will certainly not lose their reward” (vv. 41-42). Think about that: the person who “welcomes a prophet as a prophet” receives the SAME level of reward as the prophet himself: “…will receive a prophet’s reward” (v. 41).
And even if someone gives you “a cup of cold water to a disciple” that person receives a reward.
So even beyond the fellowship we have as believers in Christ, we have the promise of rewards from the Lord for helping and serving those who witness for Christ.
I think Christ is describing here the reward that comes for supporting people who serve the Lord full time in ministry. If you welcome missionaries or other servants of the Lord into your home for a meal or for lodging, Christ promises rewards for you. If you give monthly financial support to missionaries and other servants of Christ, Jesus says you will be rewarded.
You may not be able to give much. “A cup of cold water” (v. 42) is not much. But the gift is an expression of the heart that loves God and his people.
Do you give financially to support missionaries? If you think that you have too little to give to make a difference, reconsider that based on this passage. God rewards those who love him and show it by supporting and providing for his servants.