Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) said: Once we were on a journey with the beloved Prophet (peace and blessings be upon him) when suddenly a man came on his mount and began to strike to the right and to the left. So the Messenger of Allah (peace and blessings be upon him) said: "Whoever has a spare mount, let him give it to the one who has no mount, and whoever has spare provisions, let him give them to the one who has no provisions." Then he (peace and blessings be upon him) mentioned some kinds of wealth, until we thought that none of us had any right to anything surplus.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7782