Musnad Ahmad 595:8

Musa ibn Dawud narrated to us, Ibn Lahi'ah narrated to us, from Ibn Hubayrah and al-Harith ibn Yazid, from Abd al-Rahman ibn Jubayr, who said: I heard al-Mustawrid ibn Shaddad saying: I heard the Prophet, peace and blessings of Allah be upon him, saying: "Whoever is appointed to a task for us and does not have a dwelling, let him take a dwelling; or if he does not have a wife, let him marry; or if he does not have a servant, let him take a servant; or if he does not have a mount, let him take a mount. And whoever acquires anything beyond that, then he is a misappropriator (ghal)."