Srimad Bhagavatam Canto 10, Chapter 86, Text 47

SB 10.86.47

hrdi-stho ’py ati-dura-sthah
atma-saktibhir agrahyo
 ’py anty upeta-gunatmanam
But although You reside within the heart, You are very far away from those whose minds are disturbed by their entanglement in material work. Indeed, no one can grasp You by his material powers, for You reveal Yourself only in the hearts of those who have learned to appreciate Your transcendental qualities.
The all-merciful Lord is in everyone’s heart. Seeing Him there, however, is possible only when one’s heart is completely purified. Materialists may demand that God prove His existence by coming into view as a result of their empirical investigations, but God has no need to respond to such impudence. As Lord Krsna states in Bhagavad-gita (7.25):
naham prakasah sarvasya
mudho ’yam nabhijanati
 loko mam ajam avyayam
“I am never manifest to the foolish and unintelligent. For them I am covered by My internal potency, and therefore they do not know that I am unborn and infallible.”
Srimad Bhagavatam Canto 10, Chapter 86, Text 46
Srimad Bhagavatam Canto 10, Chapter 86, Text 48