Padīpopama Sutta
“Monks, mindfulness of respiration is of great fruit and great benefit. How practised is it of great fruit and great benefit?
Having gone to a forest, to the root of a tree, or to an empty place, a monk sits down cross-
The Buddha then says that while he was still a Bodhisatta he frequently practised this meditation, and so enjoyed a peaceful abiding free from mental defilements.
The Buddha then advises the monks to practice this mindfulness of respiration in this way to abide in comfort, to abandon thoughts of the household life, to gain the absorptions, and to realise nibbāna.
By practising this mindfulness of respiration a monk understands the the fuel of existence is destroyed and there will be no more rebirth, just as the flame of a lamp is extinguished when the fuel runs out. S.v.317 ff.