Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said that the Messenger of Allah (peace and blessings be upon him) travelled in Ramadan and fasted until he reached Usfan; then he (peace and blessings be upon him) called for a vessel of water and drank it during the day so that the people could see him, and he (peace and blessings be upon him) broke his fast until he reached Makkah. The narrator said: Sayyiduna Ibn Abbas (may Allah be pleased with them both) used to say: The Messenger of Allah (peace and blessings be upon him) fasted on journeys and also broke the fast; so whoever wishes may fast, and whoever wishes may not.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8160