Narrated Abdullah ibn Abbas: Two men brought their dispute to the Prophet ﷺ. The Prophet ﷺ asked the plaintiff to produce evidence, but he had no evidence. So he asked the defendant to swear. He swore by Allah "There is no god but He. " The Messenger of Allah ﷺ said: Yes, you have done it, but you have been forgiven for the sincerity of the statement: "There is no god but Allah. " Abu Dawud said: This tradition means that he did not command him to make atonement
Hadith Referenceسنن ابي داود / كتاب الأيمان والنذور / 3275
Hadith Gradingالألبانی:صحيح | زبیر علی زئی:إسناده حسن
1؎ : This is evidence that major sins (kabair) are forgiven upon reciting the testimony of monotheism (kalimat al-tawhid) with sincerity.
2؎ : Because this is such a sin that cannot be expiated by any atonement (kafarah); its only expiation is repentance (tawbah). The Messenger of Allah (sallallahu alayhi wa sallam) has said «خمس ليس لهن كفارة: الشرك بالله وقتل النفس بغير حق وبهت مؤمن والفرار يوم الزحف ويمين صابرة يقتطع بها مالا بغير حق» .
Explanation & Benefits
Shaykh Umar Farooq Saeedi
Benefits and Issues: ➊ A false oath is called "yamin ghamus." That is, it is counted among the major sins (kabair) that plunge a person into sin and destruction, and there is no financial expiation (kafarah) for it. The punishment of religion and the Hereafter is a very great penalty. However, repentance (tawbah), remorse, and a firm resolve not to do so again in the future are its only expiation. ➋ On the basis of this particular incident, no Muslim should dare to swear a false oath. ➌ The Prophet Muhammad (sallallahu alayhi wa sallam) came to know through revelation (wahy) that he had sworn a false oath. Therefore, he (sallallahu alayhi wa sallam) mentioned his falsehood with complete certainty. In addition, he also explained how to make amends for it.
Source: Sunan Abu Dawood – Commentary by Shaykh Umar Farooq Saeedi, Page: 3275