It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: Delaying repayment of a debt by a wealthy person is injustice, and when any one of you is referred to a wealthy person, he should follow up with him.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 7336