Hadithcore
Musnad Ahmad 1956
sahih· Darussalam

It was narrated that Ibn ‘Abbas said,

concerning the verse "The (Prophet"s) heart lied not in what he (Muhammad(ﷺ)) saw” [an-Najm 53:11]: Muhammad saw his Lord, may He be glorified and exalted, with his heart, twice.

References1 variant
Arabic/English book
Book 25, Hadith 1956