Musnad Ahmad 30:2568

Muhammad ibn Ubayd narrated to us, he said: Dawud narrated to us, from his father, from Abu Hurayrah, from the Prophet, peace and blessings of Allah be upon him, who said: "Indeed, the most that causes people to enter the Fire are the two hollows." They said: "O Messenger of Allah, and what are the two hollows?" He said: "The private part and the mouth." He said: "Do you know what most causes people to enter Paradise? Fear of Allah and good character."