Musnad Ahmad 962:184

Abdullah said: I found in my father’s book in his own handwriting, and I think that I heard it myself from al-Hakam: Al-Hakam ibn Musa narrated to us, Isma’il ibn ‘Ayyash narrated to us, from Matrah ibn Yazid al-Kinani, from ‘Ubayd Allah ibn Zahr, from ‘Ali ibn Yazid, from al-Qasim, from Abu Umamah, that a man asked the Messenger of Allah, may Allah bless him and grant him peace: "Which charity is best?" He said: "The shade of a tent in the way of Allah, or the service of a servant in the way of Allah, or the mounting of a stallion in the way of Allah."