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."

حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، قَالَ حَدَّثَنَا جَرِيرٌ، عَنِ الأَعْمَشِ، عَنْ عُمَارَةَ بْنِ عُمَيْرٍ، عَنْ أَبِي مَعْمَرٍ، قُلْتُ لِخَبَّابٍ أَكَانَ رَسُولُ اللَّهِ ﷺ يَقْرَأُ فِي الظُّهْرِ وَالْعَصْرِ قَالَ نَعَمْ. قُلْنَا مِنْ أَيْنَ عَلِمْتَ قَالَ بِاضْطِرَابِ لِحْيَتِهِ.