User blog comment:B214/General Discussion/@comment-29963364-20161223084324/@comment-9595671-20161227222635

Remember that this a fictional work, so not everything is accurate to the concepts used as a basis. For one example in the actual bible, and unfortunately to a few people ^v^; ...Gabriel's actually a man. DxD is one of the few franchises that uses makes him a woman cause his name sounds more like a girl's name.

So you could easily say he didn't come back to life in the DxD world, died again in the Great War, or considering how he came back to life, his soul survived in the Holy Grail, which is why it's one of the three sacred gears labeled as Holy Relics.