John Wesley on Isaiah 61:3

Ashes - By ashes understand whatever is proper for days of mourning, as by beauty whatever may become times of rejoicing. Oil of joy - He calls it oil of joy in allusion to those anointings they were wont to use in times of joy, gladness for heaviness; and it is called a garment in allusion to their festival ornaments, for they had garments appropriated to their conditions, some suitable to times of rejoicing, and some to times of mourning. Called - That they may be so. Trees - That they shall be firm, solid, and well rooted, being by faith engrafted into Christ, and bringing forth fruit suitable to the soil wherein they are planted.