It is narrated from Sayyidah Umm al-Fadl (may Allah be pleased with her) that a man came and said: "O Messenger of Allah, I have married a woman, and I also have another wife, and she has claimed that she breastfed the new wife." He (peace and blessings be upon him) said: "Breastfeeding once or twice does not establish the prohibition (of marriage)."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 21491