Yahya related to me from Malik from Abu'z-Zinad from al Araj fromAbu Hurayra that the Messenger of Allah, may Allah bless him and granthim peace, said, "Delay in payment by a rich man is injustice, butwhen one of you is referred for payment to a wealthy man, let him bereferred."
USC-MSA web (English) reference: Book 31, Hadith 85
Arabic reference: Book 31, Hadith 1372