Sayyidah Asma' bint Abi Bakr (may Allah be pleased with them both) narrates, concerning the story of Abu Quhafah and a daughter of his, one of his youngest children, that she was leading him on the day of the Conquest. When she came down with him to al-Abtah, the cavalry met her, and around her neck was a necklace of silver. Some person cut it from her neck. When the Messenger of Allah (peace and blessings be upon him) entered the Mosque, Sayyiduna Abu Bakr (may Allah be pleased with him) went out and brought his father. He mentioned the hadith about his accepting Islam. Then Sayyiduna Abu Bakr (may Allah be pleased with him) stood up, took his sister by the hand and said: "I adjure you by Allah and by Islam: (return) my sister's necklace." By Allah, no one answered him. Then he said it a second time, and still no one answered him. Then he said: "O my little sister! Seek your reward with Allah for your necklace, for by Allah, trustworthiness among the people today is scarce."
This indicates that they did not take any booty, and that it was a conquest by peace; for had it been conquered by force, she and what she had with her would have been booty, and Sayyiduna Abu Bakr (may Allah be pleased with him) would not have sought her necklace.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18283