Umm Salamah reported the Prophet (ﷺ) as saying when two men were disputing over inheritance and old things:I decide between you on the basis of my opinion in cases about which no revelation has been sent down to me.
حَدَّثَنَا إِبْرَاهِيمُ بْنُ مُوسَى الرَّازِيُّ، أَخْبَرَنَا عِيسَى، حَدَّثَنَا أُسَامَةُ، عَنْ عَبْدِ اللَّهِ بْنِ رَافِعٍ، قَالَ سَمِعْتُ أُمَّ سَلَمَةَ، عَنِ النَّبِيِّ صلى الله عليه وسلم بِهَذَا الْحَدِيثِ قَالَ يَخْتَصِمَانِ فِي مَوَارِيثَ وَأَشْيَاءَ قَدْ دَرَسَتْ فَقَالَ " إِنِّي إِنَّمَا أَقْضِي بَيْنَكُمْ بِرَأْيِي فِيمَا لَمْ يُنْزَلْ عَلَىَّ فِيهِ " .
AbuDaud
The Office of the Judge (Kitab Al-Aqdiyah) • Hadith 3585