A man named Anas bin Malik (may Allah be pleased with him) narrated that he came to Madinah and went in to the Prophet (peace and blessings be upon him) for some need of his, and found the Prophet (peace and blessings be upon him) eating. He (peace and blessings be upon him) said to him: "Come close." He said: I am fasting. the Prophet (peace and blessings be upon him) said: "Allah Almighty has relieved the traveller of fasting and half of the prayer, and also the pregnant woman and the nursing woman."
Hadith Referenceالمعجم الكبير للطبراني / باب الألف / 759