"For whosoever shall give you a cup of water to drink in my name, because ye belong to Christ, verily I say unto you, he shall not lose his reward" (Mark 9:41).
Giving a cup of water to a needy brother or sister in Christ seems, on the surface, to be such a small, even insignificant act. Yet to the Lord, it is a very important deed which one day will be rewarded. Our Lord will not overlook, or dismiss as trivial, acts of mercy done in His Name. Scripture bears this out.
God will not forget. "For God is not unrighteous to forget your work and labour of love, which ye have shewed toward his name, in that ye have ministered to the saints, and do minister" (Hebrews 6:10).
The reward is "in that day." "The Lord give mercy unto the house of Onesiphorus; for he oft refreshed me. . . . The Lord grant unto him that he may find mercy of the Lord in that day: and in how many things he ministered unto me" (II Timothy 1:16,18). "In that day" refers to the judgement seat of Christ where every believer will appear to receive rewards for the good things done for Christ during his lifetime (II Corinthians 5:10).
Tribulation saints are not excluded from reward. In Matthew 25, the "righteous" (v.37) are rewarded by Christ for giving aid and comfort to those who had been greatly persecuted during the tribulation period. "Then shall the King say unto them on his right hand, Come, ye blessed of my Father, inherit the kingdom prepared for you from the foundation of the world: For I was an hungered, and ye gave me meat: I was thirsty, and ye gave me drink" (vv.34-35).
Whether in this age or in time to come, our gracious God will give rewards to those who do even the smallest acts of kindness, like giving a cup of water in the Lord's Name. NPS