Allah's Apostle said, "May Allah's mercy be on him who is lenient in his buying, selling, and in demanding back his money."
Sahih Bukhari: Volume 3, Book 34, Number 290
The Prophet said, "Faith (Belief) consists of more than sixty branches (i.e. parts). And Haya (This term "Haya" covers a large number of concepts which are to be taken together; amongst them are self respect, modesty, bashfulness, and scruple, etc.) is a part of faith."
Volume 1, Book 2, Number 8