There is, monks, this one way to the purification of beings, for the overcoming of sorrow and distress, for the disappearance of pain and sadness, for the gaining of the right path, for the realization of Nibbāna :—that is to say, the four foundations of mindfulness.
Gautama Buddha, Digha Nikaya, Sutta 22 (Mahāsatipaṭṭhāna Sutta), as translated by M. Walshe, (1987), p. 335