The Root of Failure: Unbelief
Commentators overwhelmingly agree that the disciples' inability to heal the boy was not due to a permanent loss of their God-given authority, but a temporary lapse in faith. Scholars like Gill and Aquinas note this unbelief was present not only in the disciples but also in the boy's father and the surrounding crowd. This highlights that God's power through us is not automatic or magical, but is connected to active faith.