In trying to accommodate the three visitors Avraham said: YUKACH NA ME’AT MAYIM, “Let some water be brought…”. (18,4) Rashi comments that when Avraham said “Let some water be brought…”, he did not go to bring it himself but asked that the water should be brought by means of a messenger. Because he did not do it himself but delegated the task to a messenger who was actually his son Ishmael, Rashi says when the Israelites in the Wilderness needed water it was also given through a messenger or the rock and not sent directly from Hashem as was the case with the Manna.
The Chafetz Chaim explains why it was wrong for Avraham to ask someone else to do it. First he says that hospitality is a greater Mitzvah if one does it himself and, secondly, it is a greater honor to the guests when the host himself serves them.
Rabbi Moshe Feinstein has a different explanation. Why was it wrong to tell his son to bring the water if his intention was to teach him the Mitzvah of hospitality? His answer was that if the purpose of telling his son was Chinuch, to train him in the Mitzvah, then it would have been a greater Chinuch had he brought the water himself, demonstrating that it is better to do this Mitzvah yourself than to ask someone else to do it.
When a Mitzvah is involved, it is more important for you to perform it even of you can relegate it to others.