Azzah (may Allah be pleased with her), who was the freedwoman of Abu Hazim, said that Abu Bakr (may Allah be pleased with him) addressed us, "and he forbade us to pray on pack-saddles, or he said: he forbade praying on pack-saddles."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 21235