Sayyiduna Zubayb bin Tha'labah al-Anbari (may Allah be pleased with him) says: I heard the Messenger of Allah (peace and blessings be upon him) saying: "Whoever is obliged to free a slave from the descendants of Isma'il, let him free one from Banu al-Anbar."
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 5279
Sayyiduna Zubayb bin Tha'labah al-Anbari (may Allah be pleased with him) relates that the Messenger of Allah (peace and blessings be upon him) sent out his Companions, and they took captives from Banu al-Anbar, although they were mukhadram and had already accepted Islam. So Zubayb (may Allah be pleased with him) mounted a she-camel of his, went ahead of the people (to the Prophet (peace and blessings be upon him)) and said: O Messenger of Allah, may my father and mother be sacrificed for you, your Companions have taken captives from Banu al-Anbar, although they are mukhadram and have accepted Islam. The Prophet (peace and blessings be upon him) said to him: "O Zubayb, do you have any witness to this?" He said: Yes. So Samurah bin Amr (may Allah be pleased with him) testified and Zubayb (may Allah be pleased with him) swore an oath, and the Messenger of Allah (peace and blessings be upon him) said: "Return to Banu al-Anbar everything of theirs." So everything of theirs was returned except my mother's carpet. (Sa'd says: Zirbiyyah means qatifah, that is, a thick carpet.)
Then Zubayb (may Allah be pleased with him) came to the Prophet (peace and blessings be upon him) and said: O Messenger of Allah, may my father and mother be sacrificed for you, everything of Banu al-Anbar has been returned except my mother's carpet. The Prophet (peace and blessings be upon him) said to him: "Do you know who took it?" He said: Yes. He (peace and blessings be upon him) said: "When the people come for the prayer, sit at the door of the mosque; when you see your man, hold on to him until he finishes the prayer, then I will judge justly between you and him." So Zubayb (may Allah be pleased with him) did so.
When the Messenger of Allah (peace and blessings be upon him) finished the prayer, he turned to him and said: "O Zubayb, O brother of Banu al-Anbar, what do you want to do with this captive of yours?" Zubayb (may Allah be pleased with him) began to weep, and the man was let go. He said: I want nothing but good; I seek the pleasure of Allah and His Messenger. The Messenger of Allah (peace and blessings be upon him) said to that man: "Do you have the carpet of Zubayb's mother?" He said: O Messenger of Allah, it has gone out of my hands. The Prophet (peace and blessings be upon him) said to him: "Take off your sword and give it to him, and give him a few sa' of food in addition." So he did so.
Then the Messenger of Allah (peace and blessings be upon him) drew near to Zubayb (may Allah be pleased with him) and passed his hand over his head, bringing it down to his navel. Zubayb (may Allah be pleased with him) says: I felt the coolness of the palm of the Prophet (peace and blessings be upon him) on my navel. Then he (peace and blessings be upon him) said: "O Allah, grant him pardon and well-being."
Then Zubayb (may Allah be pleased with him) went back with the sword and sold it in exchange for two young she-camels from the charity of the Prophet (peace and blessings be upon him). Those two she-camels kept giving birth with Zubayb (may Allah be pleased with him) until their number exceeded one hundred.
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 5280