Sahih Bukhari Volume 003, Book 037, Hadith Number 486.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 37. Transference of a Debt from one Person to Another (Al-Hawaala)
Narated By Abu Huraira : The Prophet said, "Procrastination (delay) in paying debts by a wealthy man is injustice. So, if your debt is transferred from your debtor to a rich debtor, you should agree."