Musnad Ahmad 30:2872

Narrated to us Ishaq, narrated to us Malik, from Abu al-Zinad, from al-A'raj, from Abu Hurairah, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "The procrastination of the wealthy is injustice. If one of you is referred to a solvent person, let him accept the referral."