Al-Matalib al-'Aliyah 3568 — Surah al-Nisa

It is narrated from Sa'id bin Jubayr (may Allah have mercy on him) that Sayyiduna al-Miqdad bin al-Aswad (may Allah be pleased with him) set out on a military expedition. They passed by a tribe of polytheists and they all fled, but one man stayed with his family and wealth and called out: "Ashhadu an la ilaha illallah (I bear witness that there is no deity worthy of worship except Allah)," but Sayyiduna al-Miqdad (may Allah be pleased with him) killed him. It was said to him: "Did you kill him while he was bearing witness to the oneness of Allah?" He replied: "He only wished to escape with his family and wealth." The people said: "Here is the Messenger of Allah (peace and blessings be upon him); ask him." So they came to him (peace and blessings be upon him) and related the whole incident, and he (peace and blessings be upon him) asked: "Did you kill him while he was bearing witness to the oneness of Allah?" He said: "O Messenger of Allah! He only wanted to flee with his wealth and family." The narrator says: Then this verse was revealed: "O you who believe, when you go forth in the way of Allah, verify," up to the words of Allah Almighty, "Thus were you before" [Surah al-Nisa: 94].
That is: you too (in Makkah) used to conceal your faith in the same way while living among the polytheists; then Allah Almighty favoured you and gave Islam dominance, so investigate and verify thoroughly.