Sa'id bin al-Musayyib (may Allah have mercy on him) said that the Messenger of Allah (peace and blessings be upon him) said: "The pledge is not to be withheld from the one who pledged it. Its gain is his and its loss is his." In one narration the wording is: "The liability is on the one who pledged it; the gain will go to him and the loss will also be counted against him."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الرهن / 11218