Sahih al-Bukhari 7355
Sahih al-Bukhari · Book 96: Holding Fast to the Qur'an and Sunnah · If the Prophet (saws) did not disapprove of something
Narrated Muhammad bin Al-Munkadir:
حَدَّثَنَا حَمَّادُ بْنُ حُمَيْدٍ ، حَدَّثَنَا عُبَيْدُ اللَّهِ بْنُ مُعَاذٍ ، حَدَّثَنَا أَبِي ، حَدَّثَنَا شُعْبَةُ ، عَنْ سَعْدِ بْنِ إِبْرَاهِيمَ ، عَنْ مُحَمَّدِ بْنِ الْمُنْكَدِرِ ، قَالَ رَأَيْتُ جَابِرَ بْنَ عَبْدِ اللَّهِ يَحْلِفُ بِاللَّهِ أَنَّ ابْنَ الصَّائِدِ الدَّجَّالُ، قُلْتُ تَحْلِفُ بِاللَّهِ. قَالَ إِنِّي سَمِعْتُ عُمَرَ يَحْلِفُ عَلَى ذَلِكَ عِنْدَ النَّبِيِّ صلى الله عليه وسلم فَلَمْ يُنْكِرْهُ النَّبِيُّ صلى الله عليه وسلم.
I saw Jabir bin `Abdullah swearing by Allah that Ibn Sayyad was the Dajjal. I said to Jabir, "How can you swear by Allah?" Jabir said, "I have heard `Umar swearing by Allah regarding this matter in the presence of the Prophet (ﷺ) and the Prophet (ﷺ) did not disapprove of it."