“Experiencing rapture, I shall breathe out,”
thus he trains himself;
“Experiencing rapture, I shall breathe in,”
thus he trains himself.”
Buddha, Anapanasati Sutta
Explanation of Anapanasati Stage Five by Buddhadasa Bhikkhu
In the present Stage, the meditator contemplates rapture rather than the breathing. Having induced rapture, the meditator maintains mindfulness so as to be aware of that rapture by way of contemplation — that is what is meant by “training oneself”.
Rapture arises because one contemplates and is aware of non-distraction through one-pointedness of mind through breathing in and out, in each of the four stages of the first Tetrad. This means rapture can arise while one is contemplating breathing in any of the four bases.
No matter whether rapture is strong or weak, it is based entirely on breathing in and out. Therefore, it has been said “Experiencing rapture I shall breathe out… shall breathe in”. Each kind of rapture here is an object of contemplation of breathings in this Stage. Let the meditator gradually train himself and induce rapture in the full sense of the term and he will be entitled to be called “one having perfection in the fifth Stage of ànàpànasati”.