Bukhari Collection: ::Book Number 4:: Hadith # 67
Narrated `Ikrima:that Ibn `Abbas told him and `Ali bin `Abdullah to go to Abu Sa`id and listen to some of his narrations; So they both went (and saw) Abu Sa`id and his brother irrigating a garden belonging to them. When he saw them, he came up to them and sat down with his legs drawn up and wrapped in his garment and said, "(During the construction of the mosque of the Prophet) we carried the adobe of the mosque, one brick at a time while `Ammar used to carry two at a time. The Prophet passed by `Ammar and removed the dust off his head and said, "May Allah be merciful to `Ammar. He will be killed by a rebellious aggressive group. `Ammar will invite them to (obey) Allah and they will invite him to the (Hell) fire."