A. Selah appears more than seventy times in the Psalms, generally placed at the end of a sentence or paragraph.
The root is sal, probably from sullam, “a ladder”; originally the root means “to heap up” or “to raise up”, e.g. heaping sheaves of corn (Jer. 1:26); or heaping up the earth to make a highway (Isaiah 57:14; 62:10).
Selah signifies, in the first place, “continually”, or “for ever”, as time is heaped upon time.
To give a few examples: “I cried to the Lord with my voice, and He heard me out of His holy hill, Selah” (continually); “Salvation belongs to the Lord: Your blessing is upon Your people, Selah” (always); “He is the King of Glory, Selah” (for ever).
But this is not the only service which this word renders in the Psalms: it denotes also a musical pause at the close of a sentence.
The chief musicians opened the Psalm vocally, and then the instrumentalists accompanied the songs with sweet sounds. The singers also had cymbals, loud sounding and high sounding, in their hands and when they arrived at the close of a sentence or paragraph, which terminated with Selah (an “elevation” or raising of the tones), the singers suspended their vocal music and used the loud cymbals. Then the leading musician gave the signal that all sounds should cease till he began the second sentence.
The Israelites could not all get inside the Temple on festival occasions, but had to stand in the outer court, and when the Selah was reached, even those who were furthest away heard the solemn raising of the tones unaccompanied with words, and in silence awaited the commencement of the next sentence.