Sayyiduna Abu al-Yasar (may Allah be pleased with him) says that the Prophet (peace and blessings be upon him) said: "Whoever would love Allah Almighty to grant him shade on the day when there will be no shade, let him give respite to one in difficulty, or waive part of his debt." The hadith of Sayyiduna Abu Qatadah (may Allah be pleased with him) has already passed, that the Prophet (peace and blessings be upon him) said: "Whoever wishes that Allah Almighty remove from him the hardships of the Day of Resurrection, let him give respite to one in difficulty or waive his debt."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 11134
Amr bin Dinar (may Allah have mercy on him) says: Sayyiduna Ibn Abbas (may Allah be pleased with them both) said that there is no harm in the debtor saying: "I will pay you before the due time, but you waive part of the debt for me."
A hadith with a connected chain (musnad) has been narrated about this, but there is weakness in its chain.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 11135
Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) says: When the Prophet (peace and blessings be upon him) ordered that the Banu al-Nadir be expelled from Madinah, some of their people came to him and said: "O Messenger of Allah! You have ordered that they be expelled, while they have debts owed to them by people (that are not yet due)." He said: "Reduce (the debts) and take early payment," or he said: "Settle your dealings quickly."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 11137