Musannaf Ibn Abi Shayba 33:89

Ibn Idris narrated to us, from al-A’mash, from ‘Amr ibn Murrah, from Abu Ja’far, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Indeed, when faith enters the heart, the heart expands and opens for it." And he mentioned this verse: "So whoever Allah wants to guide, He expands his breast to Islam." They said: "O Messenger of Allah, is there a sign for that by which it is known?" He said: "Yes: turning towards the abode of eternity, distancing oneself from the abode of deception, and preparing for death before death."