[deleted]

Yes, Psalms 22:20
https://www.biblegateway.com/passage/?search=Psalm%2022%3A20&version=NIV

It refers to enemies who would hound and attack David with sword, horn, or like a pack of wild dogs. The actual scripture was about David asking the Lord to save him from such treachery and tumult.

The movie reinterprets this as a metaphor for seeing the "dog" in the mountains, for which only Bronco Henry, Phil, and Peter could see.

It was an obvious and repeated allusion to their homosexuality (a running theme throughout the entire film)... hence you could say that it was about the power of homosexuality (since the movie implies only homosexuals could see the dog's silhouette in the mountains, and the power it projected).

Peter embraced his homosexuality, Phil did not. Hence, Peter had corralled and championed over the power of embracing his alternative lifestyle while Phil fought against it, and in doing so, caused misery and consternation; especially in the lives of his family and those around him (including Rose).

Thus, Peter took wield of the situation to remedy it of Phil's skullduggery, and had him killed using the diseased anthrax cow hide. Thus, Peter was the one who wielded the power of the dog.

It has little to do with the actual scripture, and more-so to do with the running themes throughout the film about acceptance, the director's misplaced insinuations about "toxic masculinity", and taking charge of one's fate (and those around you) by any means necessary.