It is narrated in an authenticated tradition: 'When this verse was revealed: Whomever Allah desires to guide ... , the Prophet (SAWA) was asked about the expanding of the breast and what it was. He said, 'It is a light that Allah casts into the heart of a believer and it expands the heart and broadens it.' They asked, 'Is there a sign by which this may be known?' He (SAWA) said, 'Yes, to return to the eternal realm, to shun away from the realm of delusion, and to prepare for death before it comes.'