Chapter: Spreading the Fingers during Ruku' (Bowing), and the Description of Ruku'
• I heard Ishaq say: "Whoever joins his fingers together in ruku' and does not spread them, he has innovated, and his prayer is deficient."
• And I heard Ishaq - another time - say: "When you bow, place your hands on your knees, spread your fingers, and do not raise your head nor lower it, do not be over-proud, and flatten your back."
1072 - Muhammad ibn al-Wazir al-Dimashqi narrated to us, he said: al-Walid ibn Muslim narrated to us, he said: Ibrahim ibn 'Uthman informed me, from Abu Sufyan Tarif ibn Shihab, from Abu Nadra, from Abu Sa'id al-Khudri, from the Messenger of Allah (peace and blessings of Allah be upon him), he said: "When one of you bows, let him place his palms on his knees, straighten his back, and not sag as the donkey sags."
1073 - Muhammad narrated to us, he said: al-Walid ibn Muslim narrated to us, he said: Ibn Jurayj informed me, from 'Abdullah ibn 'Uthman, from Nafi' ibn 'Abd al-Rahman, the freed slave of Thaqif, that he asked Abu Hurayrah (may Allah be pleased with him) about prayer, and he said: "Beware of the hunwah," and the hunwah is one's clutching his lower back while he is bowing.