Al-Bara’ reported: We were with the Messenger of Allah, peace and blessings be upon him, at a funeral and he was sitting beside the edge of the grave, weeping until the ground became wet. The Prophet said, “O my brethren, prepare for the likes of this.”
Source: Sunan Ibn Mājah 4195
Grade: Hasan (fair) according to Al-Albani
عَنْ الْبَرَاءِ قَالَ كُنَّا مَعَ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فِي جِنَازَةٍ فَجَلَسَ عَلَى شَفِيرِ الْقَبْرِ فَبَكَى حَتَّى بَلَّ الثَّرَى ثُمَّ قَالَ يَا إِخْوَانِي لِمِثْلِ هَذَا فَأَعِدُّوا
4195 سنن ابن ماجه كتاب الزهد باب الحزن والبكاء
3402 المحدث الألباني خلاصة حكم المحدث حسن في صحيح ابن ماجه