Musannaf Ibn Abi Shayba 9:527

Hafs narrated to us, from Khallas ibn Salih, from Bakr ibn Fa’id, that a woman came to a man who had married a woman, and she claimed that she had breastfed both of them. He came to Ali and asked him. He said, "She is your wife; there is no one who makes her forbidden to you, and if you abstain [from her], it is better." He asked Ibn Abbas, and he said the same thing.