Anas bin Sirin (may Allah have mercy on him) said: We came from Kufah with Sayyiduna Anas (bin Malik) (may Allah be pleased with him). When we reached Atat, morning came while the ground was full of mud and water, so he prayed the obligatory prayer on his mount, then said: "Before today I have never prayed an obligatory prayer on my mount."
Hadith Referenceالمعجم الكبير للطبراني / باب الألف / 676