Selah is a Hebrew word, found only in Psalms and Habakkuk.
And if you look closely at these two books, Psalms in particular, you will realize that these are meditation books......unlike others which are historical or prophetic in nature, seen?
Selah means 'measure' or 'weigh' .
So when used in the Psalms of the mighty King David, Selah calls for deep meditation!
It tells the reader to read again and weigh out the meaning of what would have been just said, seen?
e.g. Psalm 68:7;
O God, Jah Rastafari, when You went out before Your people,
When You marched through the wilderness, Selah
Here is a call for deep thought concerning what has just been said!
Selah tells you to read again until you fully understand, before proceeding to the next verse, seen?