Sahih Al Bukhari Hadith Number 2288

Narrated Abu Huraira: The Prophet (peace be upon him) said, “Procrastination (delay) in paying debts by a wealthy person is injustice. So, if your debt is transferred from your debtor to a rich debtor, you should agree.”

38  Transferance of a Debt from One Person to Another (Al-Hawaala)
Hadith number 22
Volume no 3
Chapter: 2 (If somebody’s debt are transferred to a rich debtor)