Shaqiq bin Salamah (may Allah have mercy on him) says: I saw Sayyiduna Uthman bin Affan (may Allah be pleased with him) performing ablution. Then he mentioned the complete hadith; he says: When he washed his face, he passed (his fingers) through his beard three times and said: "I saw the Messenger of Allah (peace and blessings be upon him) doing just as you have seen me doing."
(b) Muhammad bin Isma'il al-Bukhari (may Allah have mercy on him) was asked about this hadith and said: It is hasan (good). And he said: In my view, the hadith of Uthman (may Allah be pleased with him) is the most authentic report regarding passing (the fingers) through the beard.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 246