SN54.7 — Mahākappinasutta
Originating in Sāvatthi.
At that time, Venerable Mahākappina was sitting not far from the Blessed One, having folded his legs crosswise, set his body erect, and established mindfulness on itself.
The Blessed One saw Venerable Mahākappina sitting not far away, having folded his legs crosswise, set his body erect, and established mindfulness on itself.
Seeing him, he addressed the disciples: Do you see any movement or trembling in this disciples body?
Even when we see that venerable one sitting in the midst of the Sangha or sitting alone in seclusion, we do not see any movement or trembling in his body.
Disciples, when a disciple has developed and cultivated concentration to such an extent that there is neither movement nor trembling in his body, nor movement nor trembling in his mind, that disciple is an attainer of concentration at will, without trouble, without difficulty.
And what kind of concentration when developed and cultivated, leads to neither movement nor trembling in the body, nor movement nor trembling in the mind?
It is the concentration by mindfulness of breathing that when developed and cultivated, leads to neither movement nor trembling in the body, nor movement nor trembling in the mind.
And how is mindfulness of breathing developed and cultivated so that there is neither movement nor trembling in the body, nor movement nor trembling in the mind?
Here a disciple goes to the forest, to the root of a tree, or to an empty hut, sits down, folds his legs crosswise, sets his body erect, and establishes mindfulness on itself.
Mindfully he breathes in, mindfully he breathes out...
He trains thus: I shall breathe in contemplating relinquishment; he trains thus: I shall breathe out contemplating relinquishment.
It is in this way that mindfulness of breathing is developed and cultivated so that there is neither movement nor trembling in the body, nor movement nor trembling in the mind.