Sahih al-Bukhari 2514
Sahih al-Bukhari · Book 48: Mortgaging · Dispute between the mortgagor and mortgagee
Narrated Ibn Abu Mulaika:
حَدَّثَنَا خَلاَّدُ بْنُ يَحْيَى ، حَدَّثَنَا نَافِعُ بْنُ عُمَرَ ، عَنِ ابْنِ أَبِي مُلَيْكَةَ ، قَالَ كَتَبْتُ إِلَى ابْنِ عَبَّاسٍ فَكَتَبَ إِلَىَّ أَنَّ النَّبِيَّ صلى الله عليه وسلم قَضَى أَنَّ الْيَمِينَ عَلَى الْمُدَّعَى عَلَيْهِ.
I wrote a letter to Ibn `Abbas and he wrote to me that the Prophet (ﷺ) had given the verdict that the defendant had to take an oath.