Mu'jam Kabir Tabarani 1657 — Sayyiduna Jundub bin Abdullah relates

Sayyiduna Jundub bin Abdullah (may Allah be pleased with him) relates that the Prophet (peace and blessings be upon him) sent out a detachment of men and appointed Abu Ubaydah bin al-Jarrah (may Allah be pleased with him) - or Ubaydah - as their commander. When he was about to set off, he wept out of grief at parting from the Messenger of Allah (peace and blessings be upon him), and so he held back (from going). So he (peace and blessings be upon him) sent Abdullah bin Jahsh (may Allah be pleased with him) in his place as their commander, wrote a letter for him, and ordered him not to read the letter until he reached such-and-such a place, and he said: "Do not compel any of your companions to travel with you." When he read the letter, he said Inna lillahi (performed istirja'), then said: "We hear and obey Allah and His Messenger." Then he told his companions the news and read the letter to them. Two men turned back and the rest went on. They met Ibn al-Hadrami and killed him, and they did not know whether that day was in Rajab or Jumada. So the polytheists said to the Muslims: "You have killed in the sacred month!" So Allah, the Mighty and Majestic, revealed this verse: "They ask you about fighting in the sacred month" [Surah al-Baqarah: 217], to the end of the verse. Then some people said: "Even if they did not incur any sin, there is no reward for them either." So Allah, the Mighty and Majestic, revealed this verse: "Indeed, those who believed and those who emigrated and strove in the way of Allah, it is they who hope for the mercy of Allah, and Allah is Forgiving, Merciful."