Monks, concentration by Mindfulness of Breathing (Breathing Mindfulness Meditation), when developed and cultivated, leads to the full understanding of the path.

And how, Monks, is concentration by Mindfulness of Breathing (Breathing Mindfulness Meditation) developed and cultivated so that it leads to the full understanding of the path?

Here, Monks, a Monk, having gone to the forest, to the foot of a tree, or to an empty hut, sits down. Having folded his legs crosswise, straightened his body, and set up mindfulness in front of him, just mindful he breathes in, mindful he breathes out.

Breathing in long, he knows: I breathe in long; or breathing out long, he knows: I breathe out long. Breathing in short, he knows: I breathe in short; or breathing out short, he knows: I breathe out short. ...

He trains thus: Experiencing the whole body…. (Repeat as at Chapter 1)

He trains thus: Reflecting on letting go, I will breathe in;

he trains thus: Reflecting on letting go, I will breathe out.

It is in this way, Monks, that concentration by Mindfulness of Breathing (Breathing Mindfulness Meditation) is developed and cultivated so that it leads to the full understanding of the path.

(Reference: SN 54.19)

In this Teaching from Gotama Buddha, he shares how Breathing Mindfulness Meditation leads to “full understanding of the path”.