Musnad Abu Ya'la al-Mawsili 42:91

Shayban narrated to us, Abu al-Ashhab narrated to us, Abu Nadra narrated to us, from Abu Sa’id, who said: While we were on a journey with the Prophet, may Allah bless him and grant him peace, a man came on his riding beast. He began to look to the right and to the left. The Prophet, may Allah bless him and grant him peace, said: "Whoever has a surplus of a mount, let him give it to the one who has no mount; and whoever has a surplus of provisions, let him give it to the one who has no provisions." He then mentioned various types of wealth, just as he had mentioned, until we thought that none of us had any right to any surplus.