one day I prayed by the side of Anas b. Malik. He said ; Do you know why this stick is placed here ? I said : No, by Allah. He said; The Messenger of Allah ﷺ used to put his hand upon it and say: Keep straight and straighten your rows.
هَلْ تَدْرِي لِمَ صُنِعَ هَذَا الْعُودُ فَقُلْتُ لاَ وَاللَّهِ قَالَ كَانَ رَسُولُ اللَّهِ ﷺ يَضَعُ يَدَهُ عَلَيْهِ فَيَقُولُ اسْتَوُوا وَعَدِّلُوا صُفُوفَكُمْ