Sayyiduna Ju'ayl al-Ashja'i (may Allah be pleased with him) said: I took part in one of the military expeditions with the Messenger of Allah (peace and blessings be upon him), and I was riding a weak, emaciated mare of mine, so I was left behind at the very rear of the people. He caught up with me and said: "Move on, O owner of the mare!" I said: "O Messenger of Allah, she is emaciated and weak." So the Messenger of Allah (peace and blessings be upon him) raised a whip that he had with him, struck her with it and said: "O Allah, bless him in her." The narrator said: Then I found myself holding back her head lest she go ahead of the people. And he said: I sold (animals) from her offspring for twelve thousand.
Hadith Referenceالمعجم الكبير للطبراني / باب الجيم / 2159