Ata reported,

Ibn Abbas a commented on the verse "And do not say to one who offers you the greeting of peace, 'You are not a believer'" [Nisa 4:94].Ibn Abbas explained, "There was a man tending some sheep of his when a party of Muslims came upon him. He said, 'Peace be upon you,' but they killed him and took his sheep. So Allah revealed this verse concerning that, up to His words, 'seeking the fleeting gains of this world' [Nisa 4:94], meaning those sheep."The narrator noted that Ibn Abbas recited the word as Salam.

حدثني علي بن عبد الله حدثنا سفيان عن عمرو

عن عطاء

عن ابن عباس رضي الله عنهما {ولا تقولوا لمن ألقى إليكم السلام لست مؤمنا} قال قال ابن عباس كان رجل في غنيمة له فلحقه المسلمون فقال السلام عليكم فقتلوه وأخذوا غنيمته فأنزل الله في ذلك إلى قوله {تبتغون عرض الحياة الدنيا} تلك الغنيمة قال قرأ ابن عباس السلام