Sayyiduna Abu Hadrad (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) sent us towards Idam. I set out among a group of Muslims that included Abu Qatadah al-Harith bin Rib'i and Muhallim bin Jaththamah (may Allah be pleased with them). When we reached the valley floor of Idam, Amir bin al-Adbat passed by us on his camel. When he passed by us, he greeted us with salam. We held back from him, but Muhallim bin Jaththamah (may Allah be pleased with him) attacked him, killed him and took his camel and what he had with him. When we came to the Messenger of Allah (peace and blessings be upon him) and told him, Qur'an was revealed concerning us: "O you who believe, when you go forth in the way of Allah, investigate carefully, and do not say to one who greets you with peace, 'You are not a believer,' seeking the goods of the worldly life; for with Allah are abundant spoils. You yourselves were like that before, then Allah conferred His favour upon you, so investigate carefully." [Surah al-Nisa: 94]
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18268