Sahih Bukhari Volume 008, Book 078, Hadith Number 633.

Narated By Abu Dhar : I reached him (the Prophet) while in the shade of the Ka'ba; he was saying, "They are the losers, by the Lord of the Ka'ba! They are the losers, by the Lord of the Ka'ba!" I said (to myself), "What is wrong with me? Is anything improper detected in me? What is wrong with me? Then I sat beside him and he kept on saying his statement. I could not remain quiet, and Allah knows in what sorrowful state I was at that time. So I said, ' Who are they (the losers)? Let My father and mother be sacrificed for you, O Allah's Apostle!" He said, "They are the wealthy people, except the one who does like this and like this and like this (i.e., spends of his wealth in Allah's Cause)."