Musnad Abu Ya'la al-Mawsili 152:328

Dāwūd ibn Rashīd narrated to us, Baqiyyah ibn al-Walīd narrated to us, from ‘Alī ibn ‘Alī, Yūnus narrated to me, from al-Zuhrī, from ‘Ubayd Allāh ibn ‘Abd Allāh, from Ibn Mas‘ūd, who said: A man came to him and said: "Did you hear the Messenger of Allah (may Allah bless him and grant him peace) say anything regarding horses?" He said: "Yes, I heard the Messenger of Allah (may Allah bless him and grant him peace) say: 'Good is tied to the forelocks of horses until the Day of Resurrection. Buy for the sake of Allah and seek a loan for the sake of Allah.'" It was said: "O Messenger of Allah, how do we buy for the sake of Allah and seek a loan for the sake of Allah?" He said: "Say: 'We have lent [to Allah] until our shares [of spoils] arrive, and we have sold [to Allah] until Allah grants us victory.' You will continue to be in good as long as your Jihād is green [fresh/thriving]. And there will be in the end of time a people who will doubt the Jihād, so perform Jihād in their time, then go on expeditions, for the expedition on that day is green."