Hadith 7:3
Narrated Ibn Mas'ud (RA):
I heard Allah's Messenger (ﷺ) saying, "When two people who are arranging a business transaction disagree and there is no proof to arbitrate between them, the seller's word is final, or they may break the deal." [Reported by al-Khamsa and authenticated by al-Hakim].
وَعَنْ اِبْنِ مَسْعُودٍ - رضى الله عنه - قَالَ: سَمِعْتُ رَسُولَ اَللَّهِ - صلى الله عليه وسلم -يَقُولُ: { إِذَا اِخْتَلَفَ اَلْمُتَبَايِعَانِ لَيْسَ بَيْنَهُمَا بَيِّنَةٌ, فَالْقَوْلُ مَا يَقُولُ رَبُّ اَلسِّلْعَةِ أَوْ يَتَتَارَكَانِ } رَوَاهُ اَلْخَمْسَةُ, وَصَحَّحَهُ اَلْحَاكِمُ