Sunan an-Nasa'i 1596

Ishaq ibn Musa narrated to us; he said: al-Walid ibn Muslim narrated to us; he said: al-Awza‘i narrated to us; he said: al-Zuhri narrated to me, from Sa‘id ibn al-Musayyab, from Abu Hurairah, who said: ‘Umar entered while the Ethiopians were playing in the mosque. ‘Umar (may Allah be pleased with him) rebuked them, but the Messenger of Allah (peace and blessings be upon him) said: “Let them be, ‘Umar, for they are Banu Arfidah.”