It is narrated from Sayyidah Aisha (may Allah be pleased with her) that when the Messenger of Allah (peace and blessings be upon him) performed ablution, he would use water to comb through his beard.
Hadith Takhrij«حسن لغيره۔ أخرجه الحاكم: 1/ 150 ، (انظر مسند أحمد ترقيم الرسالة: 25970 ترقیم بيت الأفكار الدولية: 26497»
Brief Explanation
Benefits: … Sayyiduna Anas radi Allahu anhu narrates that when the Messenger of Allah sallallahu alayhi wa sallam performed ablution (wudu), he would take a handful of water and insert it under his chin, passing it through his beard, and would say: ((Hākaḏā amarani rabbī.)) … My Lord has commanded me to do so. (Abu Dawud: 145, Mustadrak Hakim: 1/149. This hadith is Hasan li-ghayrihi due to multiple supporting narrations.)
Hassan bin Bilal says: I saw Sayyiduna Ammar bin Yasir radi Allahu anhu perform ablution and pass his fingers through his beard, so I said: Are you passing your fingers through your beard? He replied: And what could prevent me from doing so? I saw the Messenger of Allah sallallahu alayhi wa sallam passing his fingers through his blessed beard. (Ibn Majah: 29)
It is narrated from Sayyiduna Uthman bin Affan radi Allahu anhu that the Noble Prophet sallallahu alayhi wa sallam would pass his fingers through his blessed beard. (Tirmidhi: 31)
It is thus established that the Sunnah regarding the beard is that it should be passed through (khilal) during ablution. The method is that a handful of water should be taken and inserted under the chin into the beard, and the fingers of one hand should be passed through the hair of the beard.