Musnad Ahmad 647:3

Qaran narrated to us, Sa'id al-Shaybani Abu Sinan narrated to us, from Abu Ishaq, who said: A righteous man died, and his funeral procession was taken out. When we returned, Khalid ibn 'Arfatah and Sulayman ibn Surad—both of whom had companionship [with the Prophet]—met us. They said: "You have preceded us with this righteous man." They mentioned that he had suffered from a stomach ailment, and they feared the heat for him. One of them looked at his companion and said: "Did you not hear the Messenger of Allah, peace and blessings of Allah be upon him, say: 'Whoever is killed by his stomach shall not be punished in his grave'?"