Bojjhaṅga sutta: Awakening Factors

“Mendicants, when mindfulness of breathing is developed and cultivated it’s very fruitful and beneficial. And how is mindfulness of breathing developed and cultivated to be very fruitful and beneficial? It’s when a mendicant develops mindfulness of breathing together with the awakening factors of mindfulness, investigation of principles, energy, rapture, tranquility, immersion, and equanimity, which rely on seclusion, fading away, and cessation, and ripen as letting go. Mindfulness of breathing, when developed and cultivated in this way, is very fruitful and beneficial.”