Musnad Ahmad 1156:28

Isma'il ibn Ibrahim narrated to us, he said: Hisham al-Dastawa'i narrated to us, from Yahya ibn Abi Kathir, from Abu Salamah, from Zaynab bint Umm Salamah, from Umm Salamah, that she and the Messenger of Allah (may Allah bless him and grant him peace) used to perform ghusl (ritual bathing) from a single vessel due to janabah (major ritual impurity). And he used to kiss her while he was fasting.