Merits of the Helpers in Madinah (Ansaar)
Bukhari :: Book 5 :: Volume 58 :: Hadith 192
Narrated 'Abdullah:
The Prophet recited Surat An-Najam and prostrated, and there was nobody who did not prostrate then except a man whom I saw taking a handful of pebbles, lifting it, and prostrating on it. He then said, "This is sufficient for me." No doubt I saw him killed as a disbeliever afterwards.