Musnad Ahmad 28:99

Abu Abd al-Rahman narrated to us, Sa’id narrated to us, ‘Ayyash ibn ‘Abbas narrated to me, from ‘Isa ibn Hilal al-Sadafi, from ‘Abdullah ibn ‘Amr, who said: A man came to the Messenger of Allah, peace and blessings of Allah be upon him, and said: "Teach me to recite, O Messenger of Allah." He said to him: "Recite three from those that begin with 'Alif-Lam-Ra'." The man said: "My age has advanced, my heart has become hard, and my tongue has become thick." He said: "Then recite from those that begin with 'Ha-Mim'." The man said the same as his first statement. He said: "Recite three from the 'Musabbihat' (those that begin with the glorification of Allah)." The man said the same as his statement. The man said: "But teach me, O Messenger of Allah, a comprehensive surah." So he taught him: "When the earth is shaken (Idha zulzilat al-ardu)..." until he finished it. The man said: "By the One who sent you with the truth, I will never add anything to it." Then the man turned away. The Messenger of Allah, peace and blessings of Allah be upon him, said: "The little man has succeeded, the little man has succeeded." Then he said: "Bring him to me." So he came to him, and he said to him: "I have been commanded regarding the Day of Sacrifice, which Allah has made an Eid for this nation." The man said: "What do you think if I do not possess anything except the milking-camel of my son, should I sacrifice it?" He said: "No, but you should take from your hair, trim your nails, clip your mustache, and shave your pubic hair; that is the completion of your sacrifice in the sight of Allah."