‘Amr b. Shu'aib, on his father’s authority, told that his grandfather reported the Prophet (ﷺ) as saying, “Proof lies on the plaintiff and the oath is to be sworn by the defendant.” Tirmidhi transmitted it.

عَنْ عَمْرِو بْنِ شُعَيْبٍ عَنْ أَبِيهِ عَنْ جَدِّهِ أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «الْبَيِّنَةُ عَلَى الْمُدَّعِي وَالْيَمِينُ عَلَى الْمُدَّعَى عَلَيْهِ» . رَوَاهُ التِّرْمِذِيّ