According to a well-known sacred tradition (hadith qudsi), Allah Ta'ala says: "The Heavens and the Earth cannot contain Me, but the heart of My believing Servant does contain Me."
In otherwords, it is the 'empty' heart which can contain Allah, for only realization of Allah's utter Oneness (and thus one's own none-existence) can render one a true believing servant. It is through this heart that Allah reveals Himself to Himself, so that He may contemplate Himself in His multiple manifestations. Thus, the heart acts as a type of receptacle in which Allah sees the manifest from His Essence. This heart belongs to an individual known in Sufi metaphysics as 'the perfect man (al-insan al-kamil)' that is, one who reflects the Divine Names in their totality.