Ikrimah (may Allah have mercy on him) narrates from Abdullah bin Abbas (may Allah be pleased with them both) that Aishah (may Allah be pleased with her) bought Barirah (may Allah be pleased with her) and set her free, and they had stipulated the wala' (right of inheritance from the freed slave). The Messenger of Allah (peace and blessings be upon him) ruled: "The wala' belongs to the one who sets free," and he gave her the choice. She chose herself. He (peace and blessings be upon him) separated the two of them and imposed upon her the waiting period of a free woman.
Abu Bakr (may Allah have mercy on him) said: Habban was precise in his wording "the waiting period of a free woman," because Affan bin Muslim and Amr bin Asim both narrated it and said: "and he ordered her to observe a waiting period," and they did not mention the waiting period of a free woman.
Imam Ahmad (may Allah have mercy on him) said: Likewise Hudbah narrated it from Hammam: he ordered her to observe the waiting period of a free woman.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب العدد / 15602