Sunan an-Nasa'i, Volume 4, Book 30, Hadith 3672 (DarusSalam) ⓘ

It was narrated from Shahr bin Hawshab that Ibn Ghanm mentioned that Ibn Kharijah told him that he saw the Messenger of Allah addressing the people from atop his mount, which was chewing its cud and its saliva was dripping down. The Messenger of Allah said in his Khutbah: "Allah has given each person a share of the inheritance, and it is not permissible to give bequests to an heir."

أَخْبَرَنَا إِسْمَاعِيلُ بْنُ مَسْعُودٍ، قَالَ حَدَّثَنَا خَالِدٌ، قَالَ حَدَّثَنَا سَعِيدٌ، قَالَ حَدَّثَنَا قَتَادَةُ، عَنْ شَهْرِ بْنِ حَوْشَبٍ، أَنَّ ابْنَ غَنْمٍ، ذَكَرَ أَنَّ ابْنَ خَارِجَةَ، ذَكَرَ لَهُ أَنَّهُ شَهِدَ رَسُولَ اللَّهِ صلى الله عليه وسلم يَخْطُبُ النَّاسَ عَلَى رَاحِلَتِهِ وَإِنَّهَا لَتَقْصَعُ بِجِرَّتِهَا وَإِنَّ لُعَابَهَا لَيَسِيلُ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم فِي خُطْبَتِهِ ‏ "‏ إِنَّ اللَّهَ قَدْ قَسَّمَ لِكُلِّ إِنْسَانٍ قِسْمَهُ مِنَ الْمِيرَاثِ فَلاَ تَجُوزُ لِوَارِثٍ وَصِيَّةٌ ‏" ‏‏.‏