Narrated Ibn `Abbas:
Regarding the Verse: "And say not to anyone who offers you peace (by accepting Islam), You are not a believer." There was a man amidst his sheep. The Muslims pursued him, and he said (to them) "Peace be on you." But they killed him and took over his sheep. Thereupon Allah revealed in that concern, the above Verse up to:-- "...seeking the perishable good of this life." (4.94) i.e. those sheep.
Ibn Abbas reported that some Muslims met a person with a small flock of sheep. He said: As-Salam-o-'Alaikum. They caught hold of him and killed him and took possession of his flock. Then this verse was revealed:" He who meets you and extends you salutations, don't say: You are not a Muslim" (iv. 94). Ibn 'Abbas, however, recited the word as-Salam instead of" as-Salam".