To give them beauty for ashes, the oil of joy for mourning, the garment of praise for the spirit of heaviness, that they may be called trees of righteousness, the planting of the Lord that He may be glorified.
In times of mourning it was normal to put on sackcloth and ashes. Christ replaces that with the beautiful garments of His salvation and anoints the heads with the oil of joy for those who might mourn. The garment of praise replaces the spirit of heaviness in those whose hearts may be heavy with sin or guilt. Rooted deeply in Him they were like trees, and they were made righteous by Him. And it is all to His glory! He takes our lives broken, crumbled and like piles of ashes and turns them into something beautiful for all to see! He is Jesus our Savior and Mighty King!