The Torah in Parashat Re’eh (Debarim 15:3) commands, “Et Ha’nochri Tigos,” which the Sefer Ha’hinuch, based on the Rambam, understands as requiring a creditor to claim debts owed by a gentile idolater. The creditor is not permitted to waive the debt out of grace and compassion for the debtor.
The Sefer Ha’hinuch explains that the Torah issued this command to safeguard against close relationships between Jews and idol-worshippers, so that we do not learn from or begin imitating their sinful conduct. If we act toward them with too much kindness and generosity, we might end up forging close friendships with them, to the point where we come under their pagan influence. The Torah therefore forbade waiving debts owed by idolaters. One may, however, waive a debt for pragmatic reasons, such as if he is afraid of confronting the gentile, or if he feels that waiving the debt will work to his advantage in the future. The prohibition applies only to waving the debt out of grace and compassion. According to the Rambam and Sefer Ha’hinuch, one who forgives a debt to an idolater out of compassion transgresses this affirmative command.
The Ramban disagrees with this view, and maintains that this verse does not introduce a command requiring a creditor to claim debts from gentile debtors. According to the Ramban, this verse means that whereas one is permitted to claim debts from a gentile after the end of the Shemita year, it is forbidden to claim a debt from a Jew after the end of the Shemita. This verse should be read as a “Lav Ha’ba Michlal Aseh” – a prohibition deduced from an affirmative command. The Torah allows claiming debts from a gentile, implying that it is forbidden to claim debts from a fellow Jew. In the Ramban’s view, then, one does not violate any Torah command by forgiving a debt to an idolater.