Sufism

The heart of the believer is the Throne of the Merciful

By comparing the heart to the cosmic Throne, this saying claims a physically small inner faculty has a capacity that the entire visible universe, for all its vastness, does not.

In Islamic cosmology the Throne is described as the greatest of created things, encompassing the heavens; the hadith qudsi al-Ghazali quotes in Book 21 of the Ihya, "The Marvels of the Heart," turns that image inward by having God say that His heavens and earth do not contain Him, but the heart of His believing servant does. Al-Ghazali reads this as pointing to a real capacity in the qalb, not the physical organ but the subtle spiritual center it names, to hold a form of divine self-disclosure that the entire cosmos cannot hold. Book 21 devotes itself to explaining the heart's structure in detail, arguing it possesses faculties of perception beyond the ordinary senses. The comparison sets the stakes for the rest of the book: what happens to this small organ matters on a cosmic scale.

Ihya Ulum al-Din