Narrated Abu Ma`mar: We said to Khabbab "Did Allah's Apostle used to recite in Zuhr and `Asr prayers?" He replied in the affirmative. We said, "How did you come to know about it?" He said, "By the movement of his beard."
Hadith ReferenceSahih Bukhari / The Book of Adhan (Sufa-tus-Salat) / Hadith: 777
Hadith Gradingمحدثین:أحاديث صحيح البخاريّ كلّها صحيحة