Imam al-Shafi'i (may Allah have mercy on him) said: "The two sons of Sa'yah al-Qurazi accepted Islam while the Messenger of Allah (peace and blessings be upon him) was besieging Banu Qurayzah, and their Islam secured their lives and their property, that is, their date-palm orchards, land and other things."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / Q18262
Nafi' narrates from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that the Jews of Banu al-Nadir and Banu Qurayzah waged war against the Prophet (peace and blessings be upon him). So the Prophet (peace and blessings be upon him) exiled Banu al-Nadir, while he let Banu Qurayzah stay and showed them favour, but later Banu Qurayzah fought against him (peace and blessings be upon him). He (peace and blessings be upon him) killed their men and divided their women, property and children among the Muslims, except for those who joined the Messenger of Allah (peace and blessings be upon him); he gave them protection, and they accepted Islam.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18262
Asim bin Umar bin Qatadah narrates from an elder of Banu Qurayzah that he said: Do you know what led to the Islam of Tha'labah and Usayd (may Allah be pleased with them both), the two sons of Sa'yah, and of Asad bin Ubayd (may Allah be pleased with him), a group from (Banu) Hadl who were not of Banu Qurayzah or Banu al-Nadir but were above that? I said: No. He said: A Jewish man from Syria called Ibn al-Hayban came to us and stayed with us. By Allah, we never saw a man who did not pray the five prayers better than him. He came to us two years before the sending of the Messenger of Allah (peace and blessings be upon him). Whenever we suffered drought and rain was scarce for us, we would say to him: O Ibn al-Hayban, come out and pray for rain for us. He would say: No, by Allah, not until you give charity before you go out. We would ask: How much shall we give? He would say: A sa' of dates or two mudd of barley. Then he would go out to the open part of our lava plain, and we with him, and he would pray for rain. By Allah, he would not rise from his place before the ravines were flowing. He did this many times, not twice or three times. When death came to him, we gathered around him, and he said: O company of Jews, what do you think brought me out of the land of wine and bread to the land of hardship and hunger? We said: You know best. He said: What brought me out was only that I am awaiting the appearance of a prophet whose time has drawn near; this land is the place to which he will emigrate, so that I might follow him. So, O company of Jews, let no one get to him before you when he appears, for he will shed the blood of those who oppose him and take their children and women captive; let that not hold you back from him. Then he died. On the night when Banu Qurayzah were conquered, those three young men, who were youths of tender age, said: O company of Jews, this is the one Ibn al-Hayban mentioned to you. They said: It is not him. They said: Yes indeed, by Allah, it is him, O company of Jews; by Allah, it is him, according to his description. Then they came down, accepted Islam, and left behind their wealth, their children and their families. The narrator said: Their wealth was in the fortress with the polytheists, and when it was conquered, it was returned to them.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18263
Uthman bin Abi Hazim narrates from his father, from his grandfather Sakhr (may Allah be pleased with him), that the Messenger of Allah (peace and blessings be upon him) made an expedition against (Banu) Thaqif. When Sakhr (may Allah be pleased with him) learned of it, he rode out with horsemen to help the Prophet (peace and blessings be upon him). He found that the Prophet (peace and blessings be upon him) had returned (without a conquest), so Sakhr (may Allah be pleased with him) said: "He will not leave until these people submit to the judgement of the Messenger of Allah (peace and blessings be upon him)." Eventually they submitted to the judgement of the Prophet (peace and blessings be upon him), and Sakhr (may Allah be pleased with him) wrote (to him (peace and blessings be upon him)): "To proceed: O Messenger of Allah, they have submitted to your judgement, and they are coming to you as a party." He (peace and blessings be upon him) ordered the call "al-Salatu jami'ah" (the prayer gathers, that is, everyone should assemble) to be made, then he (peace and blessings be upon him) made ten supplications for the people of Ahmas: "O Allah, bless the people of Ahmas in their horsemen and their foot soldiers." When the people came, al-Mughirah (may Allah be pleased with him) said: O Messenger of Allah, Sakhr (may Allah be pleased with him) has taken my paternal aunt captive, and she has become Muslim along with the people. He (peace and blessings be upon him) called Sakhr (may Allah be pleased with him) and said: "O Sakhr, when people accept Islam, they secure their blood and their property, so return his aunt to al-Mughirah." Sakhr (may Allah be pleased with him) returned her to him, and he asked about the springs of Banu Sulaym, whose owners had fled from Islam and abandoned the water, (requesting) that he (peace and blessings be upon him) grant it to him and his people. He (peace and blessings be upon him) said: "Very well." They went there, and then the people of Banu Sulaym came having become Muslim. They demanded their water from Sakhr (may Allah be pleased with him), but he refused. They came to the Prophet (peace and blessings be upon him) and said: O Messenger of Allah, we have accepted Islam, and we asked Sakhr to return our water to us, but he refused. He (peace and blessings be upon him) called Sakhr (may Allah be pleased with him) and said: "O Sakhr, when people accept Islam, they secure their blood and their property, so return their water to them." He said: Very well, O Prophet of Allah. (The narrator said:) I saw the blessed face of the Messenger of Allah (peace and blessings be upon him) turning red out of modesty, because he had taken back from him both the slave woman and the water.
The Shaykh said: The evidence is drawn from his saying: "When people accept Islam, they secure their blood and their property." As for taking the water back from Sakhr (may Allah be pleased with him), it seems to have been with his willing consent, which is why the blessed face of the Messenger of Allah (peace and blessings be upon him) changed out of modesty. As for the aunt of al-Mughirah (may Allah be pleased with him), if she accepted Islam after being taken captive, then it is as though he (peace and blessings be upon him) regarded her Islam before the division as securing her property; and it is also possible that she accepted Islam before she was taken. The story of Ri'yah al-Suhaymi is similar: when he became Muslim, he said: O Messenger of Allah, my family and my property? He (peace and blessings be upon him) said: "As for your property, it has been divided among the Muslims; but as for your family, see whom of them you can reach." So his son was returned to him. It is also possible that those who had won the spoils returned him willingly.
The chain of both hadiths is not strong.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18264