Hisham bin Urwah (may Allah have mercy on him) narrates from his father (may Allah have mercy on him) that he heard Asma bint Abi Bakr (may Allah be pleased with her) say: My mother came to me during the time of the treaty with Quraysh, and she was desirous (of my kindness). So I asked the Messenger of Allah (peace and blessings be upon him): Shall I maintain ties with her? He (peace and blessings be upon him) said: "Yes." Sufyan (may Allah have mercy on him) said: It was concerning her that this verse was revealed: "Allah does not forbid you regarding those who have not fought you" [Surah al-Mumtahanah: 8].
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7844