Musnad Abu Ya'la al-Mawsili 108:88

Abu Hammam narrated to us, al-Mughirah ibn Saqlab narrated to us, Ma'qil ibn 'Ubayd Allah informed us, from 'Amr ibn Dinar, from Jabir ibn 'Abd Allah, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Whoever guarantees for me what is between his two jaws and what is between his two legs, I guarantee Paradise for him."