Narrated Abu Huraira:
The Prophet was asked about donkeys and he replied, “Nothing has been revealed to me regarding donkeys except this comprehensive Verse which includes everything: “So whoever does good equal to the weight of an atom (or a smallest ant) shall see it; And whoever,
does evil equal to the weight of an atom or a smallest ant) shall see it.’ (99.7-8)
Sahih Bukhari, Volume 6, Book60, Number 487