Albert Barnes Commentary Mark 9:41

"For whosoever shall give you a cup of water to drink, because ye are Christ`s, verily I say unto you, he shall in no wise lose his reward." — Mark 9:41 (ASV)

Whosoever shall give you a cup, etc. How easy it is to be a Christian! What is easier than to give a cup of cold water to a thirsty disciple of Jesus! But it must be in his name—that is, because he is a Christian, and therefore from love to the Saviour. This is very different from giving it from a mere motive of common kindness.

If done from love to Christ, it will be rewarded. From this we learn that the humblest acts of Christians, the lowest service that is performed, will be graciously noticed by Jesus and rewarded. No one is so humble in his kingdom that they cannot do good; and no one so poor that, in their circumstances, they cannot show the merit they attach to him. Their feeblest service will be accepted; and acts of love that may be forgotten by people will be remembered by him and rewarded in heaven.