As-Salaam alaikum,
We have it in ayat 16 of Surat Kahfi of the Holy Qur'an, where Allah Ta'ala says :

"WHEN YOU TURN AWAY FROM THEM AND THE THINGS THEY WORSHIP OTHER THAN ALLAH, BETAKE YOURSELF TO THE CAVE: YOUR LORD WILL SHOWER HIS MERCIES ON YOU.." (18:16)

The "cave" is the Divine Presence
Here one utters the cherished prayer of the Prophet Muhammad, Sallallahu alaihi Wasallam, when he prayed : "Ilahi anta maqsudi, wa ridhaka matlubi.. O God, You are my destination and Your pleasure is what I seek."

The heart, as it cycles between breathing-in and breathing-out, exists at the level of the Essence of the Divine Presence. Because that Divine Essence is the source of all created things, that heart will be at one with every minutest creation in the universe.
The highly enlightened and attentive heart will be able to see everything, hear everything, know everything, taste everything, sense everything, 'Until He will be the ears with which he hears, the eyes with which he sees, the tongue with which he speaks, the hand with which he grasps and the feet with which he walks. He will be Rabbani (Lordly), he only needs to say to a thing Kun Fayakun (Be! and it will be). "