When one thing, mendicants, is developed and cultivated the body and mind become tranquil, thinking and considering settle down, and all of the qualities that play a part in realization are fully developed. What one thing? Mindfulness of the body.”
“One thing, mendicants, when developed and cultivated leads to the realization of the fruit of stream-entry … once-return … non-return … perfection. What one thing? Mindfulness of the body.”
AN 1.575–615 Mindfulness of the Body (Bhikkhu Sujato)