Albert Barnes Commentary Psalms 68:3

"But let the righteous be glad; let them exult before God: Yea, let them rejoice with gladness." — Psalms 68:3 (ASV)

But let the righteous be glad - That is, let them be prosperous and happy; let them be under your protecting care, and partake of your favor. While the wicked are driven away like smoke, let the righteous live, and flourish, and be safe. Compare (Psalms 32:11).

Let them rejoice before God - In the presence of God; or as admitted to His presence. The wicked will be driven far off; the righteous will be admitted to His presence, and will rejoice before Him.

Yea, let them exceedingly rejoice - Margin, as in Hebrew, rejoice with gladness. The expression is designed to express great joy; joy that is multiplied and prolonged. It is joy of heart accompanied with all the outward expressions of joy.