Bhojājānīya Jātaka (No.23)
The Bodhisatta was once born as a thoroughbred horse and was made the destrier of the king of Benares. He was given every kind of luxury and was shown all honour. All the king's around coveted the kingdom of Benares, and seven kings encompassed the city. At the suggestion of his ministers, the king sent out a knight on the royal destrier. Mounted on the noble steed, the knight destroyed six camps, when his horse was wounded. He thereupon took it to the gate, loosened its armour, and prepared to arm another horse. But the animal, knowing that no other horse could accomplish what awaited him, insisted on attacking the seventh camp. Then when they brought him back to the king's gate, the king came out to look upon him, and the horse died with a counsel for mercy towards the captive kings.
The story was told in reference to a monk who had given up persevering. Ananda is identified with the king. J.i.178 81. Cp. the Ajañña Jātaka.