I wrote a letter to Ibn ʿAbbas and he wrote to me that the Prophet ﷺ had given the verdict that the defendant had to take an oath.  

أَنَّ النَّبِيَّ ﷺ قَضَى أَنَّ الْيَمِينَ عَلَى الْمُدَّعَى عَلَيْهِ  

Abdullah (bin Mas'ud) said, "Whoever took a false oath in order to grab somebody's property will meet Allah while Allah will be angry with him." Allah revealed the following verse to confirm that:--"Verily! Those who purchase a small gain at the cost of Allah's covenant And their oaths...a painful torment." (3.77) Al-Ash'ath bin Qais came to us and asked as to what Abu Abdur-Rehman (i.e. Ibn Mas'ud) was telling you." We related the story to him. On that he said, "He has told the truth. This verse was revealed about me. I had some dispute with another man regarding a well and we took the case before Messenger of Allah ﷺ. Messenger of Allah ﷺ said (to me), "Produce two witnesses (to support your claim); otherwise the defendant has the right to take an oath (to refute your claim).' I said, 'The defendant would not mind to take a false oath." Messenger of Allah ﷺ then said, 'Whoever took a false oath in order to grab someone else's property will meet Allah, Allah will be angry with him.' Allah then revealed what Confirmed it." Al-Ash'ath then recited the following Verse:--"Verily! Those who purchase a small gain at the cost of Allah's covenant, And their oaths . . . (to) . . . they shall have a painful torment!' (3.77) (See Hadith No. 546)  

فَحَدَّثْنَاهُ قَالَ فَقَالَ صَدَقَ لَفِيَّ وَاللَّهِ أُنْزِلَتْ كَانَتْ بَيْنِي وَبَيْنَ رَجُلٍ خُصُومَةٌ فِي بِئْرٍ فَاخْتَصَمْنَا إِلَى رَسُولِ اللَّهِ ﷺ فَقَالَ رَسُولُ اللَّهِ ﷺ شَاهِدُكَ أَوْ يَمِينُهُ قُلْتُ إِنَّهُ إِذًا يَحْلِفُ وَلاَ يُبَالِي فَقَالَ رَسُولُ اللَّهِ ﷺ مَنْ حَلَفَ عَلَى يَمِينٍ يَسْتَحِقُّ بِهَا مَالاً هُوَ فِيهَا فَاجِرٌ لَقِيَ اللَّهَ وَهْوَ عَلَيْهِ غَضْبَانُ فَأَنْزَلَ اللَّهُ تَصْدِيقَ ذَلِكَ ثُمَّ اقْتَرَأَ هَذِهِ الآيَةَ {إِنَّ الَّذِينَ يَشْتَرُونَ بِعَهْدِ اللَّهِ وَأَيْمَانِهِمْ ثَمَنًا قَلِيلاً} إِلَى {وَلَهُمْ عَذَابٌ أَلِيمٌ}