It is narrated from Sayyiduna Anas bin Malik (may Allah be pleased with him) that some men of the Ansar sought permission from the Messenger of Allah (peace and blessings be upon him), saying: O Messenger of Allah, permit us to waive the ransom of our sister's son, al-Abbas. The Messenger of Allah (peace and blessings be upon him) said: "By Allah, do not leave even a single dirham."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الفيء والغنيمة / 12848