"كان إذا توضأ أخذ كفا من ماء فأدخله تحت حنكه فخلل به لحيته وقال: هكذا أمرني ربي"
It was the practice of the Prophet (peace and blessings be upon him):
"When he (peace and blessings be upon him) performed ablution, he would take a handful of water, bring it under his chin and run it through his beard, and he would say: My Lord has commanded me to do so."
Hadith Referenceصحیح الجامع الصغیر / حرف الكاف / 4696
Hadith Gradingالألبانی:صحيح
Hadith Takhrij[د ك] عن أنس. المشكاة ٤٠٨، صحيح أبي داود ١٣٣.