Mishkat al-Masabih
‘Uthman said that the Prophet (ﷺ) used to make the water go through his beard. Tirmidhi and Darimi transmitted it.
وَعَنْ عُثْمَانَ رَضِيَ اللَّهُ عَنْهُ: أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ كَانَ يُخَلِّلُ لِحْيَتَهُ. رَوَاهُ التِّرْمِذِيّ والدارمي
Reference