Mark 9:41

The connecting idea with what precedes is the "name." Not only would the exorcist receive God’s blessing, but anyone who does anything to help another person using even the name of a disciple of Jesus would receive His reward. This help extends to the almost insignificant act of giving a cup of cold water to some thirsty person. This act was much less helpful than delivering from demonic affliction.

This is one of the rare occasions when Jesus used the title "Messiah" of Himself. His use of it here makes the lesson even more forceful. The person giving the cup of cold water might have only a superficial understanding of Jesus. Nonetheless if that person offered simple hospitality to one of Jesus’ disciples because he was a disciple of "Messiah" that one would receive God’s blessing.