Abu Dawud Book 3, Hadith Number 1679.

Narated By Abdullah ibn Amr ibn al-‘As : The Prophet (PBUH) said: There are forty characteristics; the highest of them is to give a goat on loan (for benefiting from its milk). If any man carries out any of those characteristics with the hope of getting a reward and testifying to the promise for it, Allah will admit him to Paradise for it.