http://www.accesstoinsight.org/tipitaka/an/an04/an04.041.than.html
AN 4.41
PTS: A ii 44
Samadhi Sutta: Concentration
translated from the Pali by
Thanissaro Bhikkhu
© 1997–2012
"Monks, these are the four developments of concentration. Which four? There is the development of concentration that, when developed & pursued, leads to a pleasant abiding in the here & now. There is the development of concentration that, when developed & pursued, leads to the attainment of knowledge & vision. There is the development of concentration that, when developed & pursued, leads to mindfulness & alertness. There is the development of concentration that, when developed & pursued, leads to the ending of the effluents.
"And what is the development of concentration that, when developed & pursued, leads to a pleasant abiding in the here & now? There is the case where a monk — quite withdrawn from sensuality, withdrawn from unskillful qualities — enters & remains in the first jhana: rapture & pleasure born from withdrawal, accompanied by directed thought & evaluation. With the stilling of directed thoughts & evaluations, he enters & remains in the second jhana: rapture & pleasure born of composure, unification of awareness free from directed thought & evaluation — internal assurance. With the fading of rapture, he remains equanimous, mindful, & alert, and senses pleasure with the body. He enters & remains in the third jhana, of which the Noble Ones declare, 'Equanimous & mindful, he has a pleasant abiding.' With the abandoning of pleasure & pain — as with the earlier disappearance of elation & distress — he enters & remains in the fourth jhana: purity of equanimity & mindfulness, neither pleasure nor pain. This is the development of concentration that, when developed & pursued, leads to a pleasant abiding in the here & now.
"And what is the development of concentration that, when developed & pursued, leads to the attainment of knowledge & vision? There is the case where a monk attends to the perception of light and is resolved on the perception of daytime [at any hour of the day]. Day [for him] is the same as night, night is the same as day. By means of an awareness open & unhampered, he develops a brightened mind. This is the development of concentration that, when developed & pursued, leads to the attainment of knowledge & vision.
"And what is the development of concentration that, when developed & pursued, leads to mindfulness & alertness? There is the case where feelings are known to the monk as they arise, known as they persist, known as they subside. Perceptions are known to him as they arise, known as they persist, known as they subside. Thoughts are known to him as they arise, known as they persist, known as they subside. This is the development of concentration that, when developed & pursued, leads to mindfulness & alertness.
"And what is the development of concentration that, when developed & pursued, leads to the ending of the effluents? There is the case where a monk remains focused on arising & falling away with reference to the five clinging-aggregates: 'Such is form, such its origination, such its passing away. Such is feeling, such its origination, such its passing away. Such is perception, such its origination, such its passing away. Such are fabrications, such their origination, such their passing away. Such is consciousness, such its origination, such its disappearance.' This is the development of concentration that, when developed & pursued, leads to the ending of the effluents.
"These are the four developments of concentration.
"And it was in connection with this that I stated in Punnaka's Question in the Way to the Far Shore [Sn 5.3]:
'He who has fathomed the far & near in the world, for whom there is nothing perturbing in the world — his vices evaporated, undesiring, untroubled, at peace — he, I tell you, has crossed over birth aging.'"
I had a thought in mind "I wonder if there are some clear teachings on the practice of samadhi".
Then synchronistically I saw this sutta just a moment after this thought. It is very clear indeed.