Musnad Abu Ya'la al-Mawsili 214:2

Zuhayr narrated to us, Isma'il bin Ibrahim narrated to us, from Ayyub, from Abu al-Khalil, from 'Abdullah bin al-Harith, from Umm al-Fadl, who said: A man came to the Prophet, may Allah bless him and grant him peace, while he was in my house, and said: "I had a wife, and I married another woman over her. My first wife claimed that she had breastfed the younger one once or twice." He said: "One or two sucklings do not make [the marriage] unlawful."