Musnad Ahmad 498:7

Rawh narrated to us, Shu'bah narrated to us, from 'Abd Rabbih ibn Sa'id, from Ibn Abi Anas, from 'Abdullah ibn Nafi' ibn al-'Amya', from 'Abdullah ibn al-Harith, from al-Muttalib, that the Prophet (peace and blessings of Allah be upon him) said: "The prayer is two by two; you recite the Tashahhud in every two rak'ahs, and you show distress, and you show humility, and you raise your hands, and you say: 'O Allah, O Allah.' Whoever does not do that, it is deficient (khidaj)." Shu'bah said: "I said: 'His prayer is deficient?' He said: 'Yes.' I said to him: 'What is al-iqna' (raising the hands)?' So he spread out his hands as if he were supplicating."