Hadith 4:182
He said that the Prophet’s grave was sprinkled and that the one who sprinkled the water over his grave from a water-skin was Bilal b. Rabah. He began where the head was and sprinkled it to his feet. Baihaqi transmitted it in Dalail an-nubuwa .
وَعَن جَابر قَالَ: رُشَّ قَبْرُ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ وَكَانَ الَّذِي رَشَّ الْمَاءَ عَلَى قَبْرِهِ بِلَالُ بْنُ رَبَاحٍ بِقِرْبَةٍ بَدَأَ مِنْ قِبَلِ رَأْسِهِ حَتَّى انْتَهَى إِلَى رِجْلَيْهِ. رَوَاهُ الْبَيْهَقِيُّ. فِي دَلَائِل النُّبُوَّة
Original Reference: Mishkat al-Masabih 1710