Musnad Ahmad 1153:899

'Affan narrated to us, he said: Muhammad ibn Dinar narrated to us, from Sa'd ibn Aws, from Musda' Abu Yahya al-Ansari, from 'Aisha: "That the Messenger of Allah, peace and blessings of Allah be upon him, used to kiss her while he was fasting, and he would suck her tongue." I said: "Did you hear it from Sa'd ibn Aws?" He said: "Yes."