Musannaf Ibn Abi Shayba 3:4782

Waki’ narrated to us, he said: Muhammad bin Qays narrated to us, from Ali bin Mubarak, that when Mu’adh arrived in Yemen, he was teaching the [tribe of] Nakha’. He said to them: "When you see me do something in the prayer, then do the same." When he prostrated, a tree branch struck his eyes, so he broke it while in the prayer. Every man among them then proceeded to a branch while in the prayer and broke it. When he finished the prayer, he said: "I only broke it because it struck my eyes when I prostrated, and you have done well in that you obeyed."