Psalms 99:3

Let them praise thy great and terrible name - Let them confess thee to be great and terrible: let them tremble before thee.

For it is holy - הוא קדוש kadosh hu . As this not only ends this verse but the fifth also, and in effect the ninth, it seems to be a species of chorus which was sung in a very solemn manner at the conclusion of each of these parts. His holiness - the immaculate purity of his nature, was the reason why he should be exalted, praised, and worshipped.