New Defender's Study Bible Notes
3:21 his glorious body. These “vile” bodies in which we now reside are subject to decay and death, along with the entire creation (Romans 8:20-22), but they will be instantaneously glorified and made like His body of glory when Christ returns (I Corinthians 15:51-54; Romans 8:21; I John 3:2).
3:21 working. This “working” (Greek energeia) could be effectively paraphrased as “creative energizing.” He who is the Creator of all the energy and matter of the universe (actually, even matter is a form of energy) is able to create new energy and matter to resurrect dead bodies and glorify living bodies to make them like His own eternally living resurrected body, no longer subject to decay and pain and death.