Hadith 8:2541
Abu Bakr narrated to us, he said: Waki’ narrated to us, from Sufyan, from Layth, who said: A woman who traveled with her slave was mentioned to Umar ibn Abd al-Aziz. He disliked that. It was then said to him: "He is her foster-brother." So he saw no harm in it.
حدثنا أبو بكر قال نا وكيع عن سفيان عن ليث قال ذكر لعمر بن عبد العزيز امرأة سافرت مع عبدها فكره ذلك فقيل له إنه أخوها من الرضاعة فلم ير به بأسا