Musnad Ahmad 907:70

Muhammad ibn Ja‘far narrated to us, Shu‘bah narrated to us, from Sulayman, who said: I heard al-Musayyab ibn Rafi‘ narrating from Tamim ibn Tarafah, from Jabir ibn Samurah, from the Prophet, may Allah bless him and grant him peace, that he entered the mosque and saw a people who had raised their hands. He said: "They have raised them as if they were the tails of sun-struck horses. Be still in the prayer."