Sayyiduna Anas bin Malik (may Allah be pleased with him) says: We, the group of Companions, used to travel; some would shorten the prayer and break the fast, and some would pray in full and also fast. The one fasting would not find fault with the one breaking the fast, nor the one breaking the fast with the one fasting, nor the one shortening with the one praying in full, nor the one praying in full with the one shortening.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5440