Maitrayaniya Upanishad 4.4

4.4

cittasya hi prasādena hanti karma śubhāśubham |
prasannātmātmani sthitvā sukhamavyayamaśnute ||

"Brahman is," thus said one who knew the science of Brahman; and this penance is the door to Brahman, thus said one who by penance had cast off all sin. The syllable Om is the manifest greatness of Brahman, thus said one who well grounded (in Brahman) always meditates on it. Therefore by knowledge, by penance, and by meditation is Brahman gained. Thus one goes beyond Brahman (Hiranyagarbha), and to a divinity higher than the gods; nay, he who knows this, and worships Brahman by these three (by knowledge, penance, and meditation), obtains bliss imperishable, infinite, and unchangeable. Then freed from those things (the senses of the body, &c.) by which he was filled and overcome, a mere charioteer, he obtains union with the Self.'