Musnad Ahmad 28:576

Musa ibn Dawud narrated to us, Ibn Lahi'ah narrated to us, from Yazid ibn Abi Habib, from Qaysar al-Tujibi, from Abdullah ibn Amr ibn al-As, who said: We were with the Prophet, may Allah bless him and grant him peace. A young man came and said: "O Messenger of Allah, may I kiss while I am fasting?" He said: "No." Then an old man came and said: "O Messenger of Allah, may I kiss while I am fasting?" He said: "Yes." We looked at one another, so the Messenger of Allah, may Allah bless him and grant him peace, said: "I know why you looked at one another; the old man is able to control himself."