Where is the one who was swearing by Allah that he would not do a favor?

Hadīth explanation: The Prophet (may Allah's peace and blessings be upon him) heard two men arguing over a financial matter. Their voices were so loud that he heard them while he was inside his house. He listened to them and heard one of them asking the other to reduce the amount of debt that he owes him or to show him leniency in collecting it. The other man's answer was: "By Allah! I will not do that." Thereupon, the Prophet went out to them and asked who it was who was swearing by Allah that he would not do a good deed. One of the two men said: "I am that person, O Messenger of Allah. I will give him whatever he wishes."
In another narration (about debt forgiveness) reported by Ahmad and Ibn Hibbān: "The man said: 'If you wish, I will waive the amount they are short of, and if you wish, I will waive part of the original sum.' So he waived the amount they were short of."
This narration was mentioned in this chapter for an obvious reason: to indicate that the Prophet (may Allah's peace and blessings be upon him) sought reconciliation between the two disputing men, either by reducing the loan, or by showing leniency. There is a similar narration relevant to this topic that was mentioned by Al-Bukhāri and Muslim on the authority of Ka‘b ibn Mālik (may Allah be pleased with him). He reported that ‘Abdullāh ibn Abi Hadrad al-Aslami owed him money, and so when he met him and asked for his money, they argued until their voices became loud. The Prophet (may Allah's peace and blessings be upon him) passed by them and said: "O Ka‘b!" and then gestured with his hand as if he was saying "half", so Ka‘b took half of what ‘Abdullāh owed him and waived the other half.
The Muslim should strive in doing good deeds, especially in reconciling between people and easing their circumstances. If he sees two people, two groups, or two tribes disputing and fighting one another, he should seek to reconcile between them in order to remove what is causing disunity and hatred and to replace it with brotherhood and love. Doing this is more rewarding than fasting, praying, and giving charity. The Prophet (may Allah's peace and blessings be upon him) said: "Shall I not tell you of what is higher in rank than fasting, praying, and giving charity?" They said: "Yes, O Messenger of Allah." He said: "Reconciling between two parties." [Abu Dawūd; classified as Sahīh by Al-Albāni]