Majma al-Zawaid — Hadith 9708

Alqamah bin Hilal reports from his father, from his grandfather, that he came to the Prophet (peace and blessings be upon him) with some men of his people. The Prophet (peace and blessings be upon him) was in Madinah at the time; this was after he had emigrated to Madinah. We found the Prophet (peace and blessings be upon him) having the necks of captives struck beside a little water; he had them killed beside that water until the blood covered the water. Safwan said: The word safaha means that it covered the water.
Al-Tabarani recorded it. The narrator Alqamah is majhul (unknown), and before him there is a narrator who is not named.