Sahih Muslim Book 6, Hadith Number 2437.

Chapter : Kissing is not forbidden while fasting if one is not urged by sexual lust.

Sufyan reported: I said to ‘Abd al-Rahman b. Qasim: Have you heard from your father narrating from ‘Aisha (Allah be pleased with her) that he kissed her while observing fast? He (‘Abd al-Rahman b. Qasim) kept silence for a short while and then said: “Yes.”