Musnad Ahmad 30:2843

Waki' narrated to us, Sufyan narrated to us, from Abu al-Zinad, from al-A'raj, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The procrastination of the wealthy is injustice, and whoever is referred to a solvent person, let him accept the transfer."