It is written in the Torah: ‘O son of Man, if you “empty” yourself (i.e. disengage yourself from all other preoccupations to make yourself available) for My worship, I will fill your heart with richness and I will not abandon you to what you seek and long for. And it will be upon Me to close the door of poverty upon you and to fill your heart with awe for Me. And if you don’t “empty” yourself for My worship, I will fill your heart with preoccupation with the world and I will not close upon you the door of poverty and will abandon you to what you seek.
Al-Kulayni, Usul al-Kafi, ii, “kitab al-‘iman wa a1-kufr’, “bab al-`ibadah”, hadith no. 1. (via abustaif)