We said to Khabbab "Did Messenger of Allah ﷺ used to recite in Zuhr and ʿAsr prayers?" He replied in the affirmative. We said, "How did you come to know about it?" He said, "By the movement of his beard."  

عَنْ أَبِي مَعْمَرٍ قُلْتُ لِخَبَّابٍ أَكَانَ رَسُولُ اللَّهِ ﷺ يَقْرَأُ فِي الظُّهْرِ وَالْعَصْرِ قَالَ نَعَمْ قُلْنَا مِنْ أَيْنَ عَلِمْتَ قَالَ بِاضْطِرَابِ لِحْيَتِهِ