SN54.20 — The Discourse on the Destruction of the Taints
And how, disciples, is mindfulness of breathing developed and made much of so that it leads to the abandonment of the fetters... to the uprooting of latent tendencies... to the full understanding of the path... to the destruction of the taints?
Here, disciples, a disciple goes to the forest, or to the root of a tree, or to an empty place, and he trains thus: I shall breathe in contemplating relinquishment; I shall breathe out contemplating relinquishment.
Mindfulness of breathing, when developed and cultivated in this way, leads to the abandonment of the fetters... to the uprooting of latent tendencies... to the full understanding of the path... to the destruction of the taints.