“The Psalms are the steady, sustained subcurrent of healthy Christian living. They shaped the praying and vocation even of Jesus himself. They can and will do the same for us. The Psalms do this, to begin with, simply because they are poetry set to music: a classic double art form. To write or read a poem is already to enter into a different kind of thought world from our normal patterns. A poem is not merely ordinary thought with a few turns and twiddles added on to make it pretty or memorable. A poem (a good poem, at least) uses its poetic form to probe deeper into human experience than ordinary speech or writing is usually able to do, to pull back a veil and allow the hearer or reader to sense other dimensions. Sometimes”
― N.T. Wright, The Case for the Psalms: why they are essential
Selah is a word used 74 times in the Old Testament – 71 times in the Psalms and three times in Habbakuk – and is a difficult concept to translate. (It should not be confused with the Hebrew word ‘sela’ which means “rock.”)
It is probably either a liturgico-musical mark or an instruction on the reading of the text, something like “stop and listen.” Selah can also be used to indicate that there is to be a musical interlude at that point in the Psalm. The Amplified Bible translates selah as “pause, and think of that.” It can also be interpreted as a form of underlining in preparation for the next paragraph.