Musnad Abu Ya'la al-Mawsili 248:39

Al-Abbas ibn al-Walid al-Narsi narrated to us, Yahya ibn Sa'id al-Qattan narrated to us, from Sulayman, who said: al-Musayyab ibn Rafi' narrated to me, from Tamim ibn Tarfah al-Ta'i, from Jabir ibn Samurah, who said: The Messenger of Allah (may Allah bless him and grant him peace) entered the mosque while they were raising their hands. He said: "They have raised their hands as if they were the tails of restive horses. Be still in the prayer."