The Holy Prophet ﷺ said to a man whom he asked to take an oath: Swear by Allah except whom there is no god that you have nothing belonging to him, i.e. the plaintiff. (Using translation from Abū Dāʾūd 3620)
رَسُولَ ﷺ قَالَ لِرَجُلٍ حَلَّفَهُ احْلِفْ بِاللهِ الَّذِي لَا إِلَهَ إِلَّا هُوَ مَا لَهُ عِنْدَكَ شَيْءٌ يَعْنِي لِلْمُدَّعِي