Silsilat al-Ahadith al-Sahihah

Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) says: A man asked the Prophet Muhammad (peace and blessings be upon him) a question about prayer. The Messenger of Allah (peace and blessings be upon him) said: "Clean between the fingers of your hands and feet." By this, he meant that the ablution should be completed properly. Furthermore, the Prophet (peace and blessings be upon him) also said to him: "When you bow (in ruku‘), place your palms on your knees and be at ease in the position of ruku‘, and when you prostrate (in sujud), place your forehead firmly on the ground until you feel the thickness of the earth."