Abu Dawud Book 25, Hadith Number 3963.

Narated By Ibn ‘Abbas : The Muslims met a man with some sheep of his. He said: Peace be upon you. But they killed him and took those few sheep. Thereupon the following Qur’anic verse was revealed: “… And say not to anyone who offers you a salutation: Thou art none of a believer, coveting the perishable goods of this life,” meaning these few sheep.