Musnad Ahmad 28:407

Muhammad ibn Ja‘far narrated to us, Shu‘bah narrated to us, from Mansur, from Hilal ibn Yasaf, from Abu Yahya al-A‘raj, from ‘Abdullah ibn ‘Amr ibn al-‘As, who said: I asked the Messenger of Allah, peace and blessings of Allah be upon him, about a man’s prayer while sitting? He said: "It is half of his prayer while standing." He said: And the Messenger of Allah, peace and blessings of Allah be upon him, saw some people performing ablution who did not complete the ablution. He said: "Perform the ablution thoroughly—meaning the ablution—woe to the heels from the Fire, or: the ankles."