vayera

ויטע אשל בבאר שבע ויקרא שם בשם ה'
Avraham planted a tree & called out in the name of 'ה.
Rashi says that from this Posuk we learn that Avraham had an open house & fed all the people who came by & taught them about 'ה.
But when the Torah tells us about how  Avraham fed the Malachim it goes through every detail of how he did it & what he gave them & that he was rewarded based on how he served them.
R' Tzudok asks, wouldn't it have made more sense for the Torah to give us details on how Avraham performed chesed for actual people & how he got them into the fold to believe in 'ה than to tell us details about Malachim that didn't need his hospitality & the whole thing was just a show?
The Posuk says that Avraham told the Malachim to wash their feet.
Rashi says that he didn't give them the water himself but he had someone else do it & because of that his children would be given water from a messenger & not directly from 'ה.
R' Moshe says that we see from there that the main part of doing Chesed is not  the outcome,  but the work that goes into it. That's why he should have brought the water to the Melachim himself.
Similarly says R' Tzudok, the reason the Torah told us about Avraham's hospitality only by the Malachim was to teach us that even though Avraham's chesed to the Malachim was unnecessary & pointless to them, for him it was pure Chesed & that its the work & the intent that's in your heart that 'ה cares about & not if you actually accomplish something or not!