Sahih al-Bukhari 2711, 2712

It is related from Marwan and al-Miswar ibn Makhrama from the Companions of the Messenger of Allah, "When Suhayl ibn 'Amr wrote the document on that day, one of the preconditions which Suhayl ibn 'Amr stipulated from the Prophet, may Allah bless him and grant him peace, was: "If anyone comes to you, even if he has your deen, you will return him to us and not come between us and him.' The believers disliked that and resented it. Suhayl refused to accept anything but that, so the Prophet, may Allah bless him and grant him peace, wrote it with him on that basis. On that day he returned Abu Jandal to his father, Suhayl ibn 'Amr. Any man who came to him he returned in that period, even if he was a Muslim. Believing women came as emigrants, and Umm Kulthum bint 'Uqba ibn Abi Mu'ayt was one of those who came to them on that day.She was a young girl. Her people came to ask the Prophet, may Allah bless him and grant him peace, to return her to them, but he did not return her to them since Allah had revealed about them, 'When believing women come to you as emigrants, submit them to a test. Allah has best knowledge of their faith. If you know they are believers, do not return them to the rejectors.They are not lawful for the rejectors nor are the rejectors lawful for them.' (60:10)" It is reported from 'A'isha that the Messenger of Allah, may Allah bless him and grant him peace, used to examine them by this ayat, "O you who believe! When believing women come to you as emigrants, submit them to a test. ... to ...Ever-Forgiving, Most Merciful." (60:10-12) 'A'isha said, "Whoever of them acknowledged this precondition, the Messenger of Allah, may Allah bless him and grant him peace, would say to her, 'I have taken a contract of allegiance from you.' These are the words he used to say and, by Allah, he never touched the hand of a woman in the contract of allegiance, and he only made the contract of allegiance with them by his words."