The Messenger of Allah ﷺ said, "Whoever is owed a debt by another and grants him an extension, he will receive the reward of giving in charity for each day of the delay."
حدثنا عبد الله حدثني أبي حدثنا أسود بن عامر حدثنا أبو بكر عن الأعمش عن أبي داود
قال رسول الله ﷺ من كان له على رجل حق فمن أخره كان له بكل يوم صدقة
No references are available.
Its isnad is daif because of Abu Dawud the blind, whose name is Nufay bin Harith. They unanimously graded him daif, and Busiri said likewise in his commentary on Zawaid bin Majah. See the Sunan 2/808, no. 2418.