It is devours the enemies not the believers. He calls them to repent, he cannot deny he has paid their full wage by the incorruptible seed as those born again.(once)
For if we sin wilfully after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins,But a certain fearful looking for of judgment and fiery indignation, which shall devour the adversaries.Hebrews 10
Again it cannot devour the believer who has passed from eternal separation(death) to eternal life.