It is narrated from Abu Ma'mar (may Allah have mercy on him): We asked Khabbab bin al-Aratt (may Allah be pleased with him): Did the Messenger of Allah (peace and blessings be upon him) recite in the Zuhr and Asr prayers? He said: "Yes." We said: How did you come to know? He said: "By the movement of his (peace and blessings be upon him) blessed beard."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3060