Authentic
graded by Al-Albani
Mishkat al-Masabih 361
وَعَن الحكم بن سُفْيَان قَالَ: كَانَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِذَا بَالَ تَوَضَّأَ وَنَضَحَ فَرْجَهُ. رَوَاهُ أَبُو دَاوُد وَالنَّسَائِيّ
Al-Hakam b. Sufyan said that when the Prophet passed water he performed ablution and sprinkled his penis. Abu Dawud and Nasa’i transmitted it.
Cited in Mishkat al-Masabih (No. 361).