Selah!

Selah, a Hebrew word meaning "pause, reflection", within the context of a prayer or psalms, may be the most difficult word in the Hebrew Bible to translate. Selah is probably either a liturgico-musical mark or an instruction on the reading of the text, something like "stop and listen". The Psalms were sung accompanied by musical instruments and there are references to this in many chapters. Thirty-one of the thirty-nine Psalms with the caption "To the choir-master" include "Selah" so the musical context of selah is obvious. Selah notes a break in the song and as such is similar in purpose to “Amen” in that it stresses the importance of the preceding passage. Alternatively, Selah may mean "forever," as it does in some places in the liturgy (notably the second to last blessing of the Amidah). Its etymology and precise meaning are unknown.
This word occurs seventy-one times in thirty-nine of the Psalms, and three times in Habakkuk 3. It is found at the end of Psalms 3, 24, and 46, and in most other cases at the end of a verse, the exceptions being Psalms 55:19, 57:3, and Hab. 3:3, 9.
The significance of this term was apparently not known even by ancient Biblical commentators. This can be seen by the variety of renderings given to it. The Septuagint, Symmachus, and Theodotion translate διάψαλμα — a word as enigmatical in Greek as is "Selah" in Hebrew. The Hexapla simply transliterates σελ. Aquila, Jerome, and the Targum translate it as "always". According to Hippolytus (De Lagarde, "Novæ Psalterii Græci Editionis Specimen" 10), the Greek term διάψαλμα signified a change in rhythm or melody at the places marked by the term, or a change in thought and theme. Against this explanation Baethgen ("Psalmen," p. 15, 1st ed. Göttingen, 1892) notes that Selah also occurs at the end of some
Psalms.
Modernly, it is generally held that "Selah" has no grammatical connection. However, E. W. Bullinger believes "Selah" is a conjunction linking two verses (or thoughts, or Psalms together either in contrast, further explanation, or to mark a cause/effect relationship.
In keeping with this it has been assigned to the root, as an imperative that should properly have been vocalized , "Sollah" (Ewald, "Kritische Grammatik der Hebräischen Sprache,"p. 554; König, "Historisch-Kritisches Lehrgebäude der Hebräischen Sprache," ii., part i., p. 539). The meaning of this imperative is given as "Lift up," equivalent to "loud" or "fortissimo," a direction to the accompanying musicians to break in at the place marked with crash of cymbals and blare of trumpets, the orchestra playing an interlude while the singers' voices were hushed. The effect, as far as the singer was concerned, was to mark a pause. This significance, too, has been read into the expression or sign, "Selah" being held to be a variant of "shelah" (="pause"). But as the interchange of "shin" and "samek" is not usual in Biblical Hebrew, and as the meaning "pause" is not held to be applicable in the middle of a verse, or where a pause would interrupt the sequence of thought, this proposition has met with little favor.
Grätz argues that "Selah" introduces a new paragraph, and also in some instances a quotation (eg, Psalms 57:8 et seq. from 108:2 et seq.) The fact that the term occurs four times at the end of a Psalm would not weigh against this theory. The Psalms were meant to be read in sequence, and, moreover, many of them are fragment: .psalm 9 is reckoned one with psalm 10 in the Septuagint, which omits διάψαλμα (diapsalma) also at the end of psalms 3, 24, and 46 B. Jacob (l.c.) concludes (1) that since no etymological explanation is possible, "Selah" signifies a pause in or for the Temple song; and (2) that its meaning was concealed lest the Temple privileges should be obtained by the synagogues or perhaps even by the churches.
"Selah" is also used in Iyaric (Rastafarian vocabulary); it can be heard at the end of spoken-word segments of some reggae songs. Its usage here, again, is to accentuate the magnitude and importance of what has been said, and often is a sort of substitute for Amen. The Iyaric term has also been said by folk etymology to signify "Seal up" as in, "may JAH seal up any inadvertent mistakes in what was said".
Selah is also the title of two songs of instrumental worship and spoken prayer by Hillsong United, named respectively Selah 1 and Selah 2, on their 2006 United We Stand album.
In Hunter S. Thompson's collected works "Songs of the Doomed" the word "Selah" is used frequently in letters and diatribes written from the 1960s to the 1990s. The word is used similarly to the word "Allora" in Italy. It is also akin to Kurt Vonnegut's use of the phrase "So it goes" in his novel Slaughterhouse-Five.

And after we pray, what better than to stop and listen? Selah!