Sahih al-Bukhari, Volume 1, Book 12, Hadith 713 (USC-MSA) ⓘ

Narrated Abu Ma`mar: We asked Khabbab whether Allah's Messenger used to recite (the Qur'an) in the Zuhr and the `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."

حَدَّثَنَا مُوسَى، قَالَ حَدَّثَنَا عَبْدُ الْوَاحِدِ، قَالَ حَدَّثَنَا الأَعْمَشُ، عَنْ عُمَارَةَ بْنِ عُمَيْرٍ، عَنْ أَبِي مَعْمَرٍ، قَالَ قُلْنَا لِخَبَّابٍ أَكَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يَقْرَأُ فِي الظُّهْرِ وَالْعَصْرِ قَالَ نَعَمْ‏.‏ قُلْنَا بِمَ كُنْتُمْ تَعْرِفُونَ ذَاكَ قَالَ بِاضْطِرَابِ لِحْيَتِهِ‏.‏