He now says “He gives his authority to no one other than God. To think otherwise is believing in a false idol. This is laid out in the Ten Commandments.”
So Jesus gives authority to Peter in Matt 16:18. Also previously when he told Peter to feed my sheep. What other verses can I use to show this?
A partial list, but it may help the conversation:
Authority Given by God to Men to Rule His People:
Num. 27[18] And the LORD said to Moses, "Take Joshua the son of Nun, a man in whom is the spirit, and lay your hand upon him; [19] cause him to stand before Elea’zar the priest and all the congregation, and you shall commission him in their sight. [20] You shall invest him with some of your authority, that all the congregation of the people of Israel may obey.
Mt. 10[1] And he called to him his twelve disciples and gave them authority over unclean spirits, to cast them out, and to heal every disease and every infirmity.
Mk. 6[7] And he called to him the twelve, and began to send them out two by two, and gave them authority over the unclean spirits
2Cor. 10[8] For even if I boast a little too much of our authority, which the Lord gave for building you up and not for destroying you, I shall not be put to shame.
2Cor. 13[10] I write this while I am away from you, in order that when I come I may not have to be severe in my use of the authority which the Lord has given me for building up and not for tearing down.
Tit. 2[15] Declare these things; exhort and reprove with all authority. Let no one disregard you.
Num. 27[16] "Let the LORD, the God of the spirits of all flesh, appoint a man over the congregation,
Deut. 7[13] Choose wise, understanding, and experienced men, according to your tribes, and I will appoint them as your heads.’
Deut. 16[18] "You shall appoint judges and officers in all your towns which the LORD your God gives you, according to your tribes; and they shall judge the people with righteous judgment.
Ezra 7[25a] "And you, Ezra, according to the wisdom of your God which is in your hand, appoint magistrates and judges who may judge all the people…
Acts 6[3] Therefore, brethren, pick out from among you seven men of good repute, full of the Spirit and of wisdom, whom we may appoint to this duty.
Acts 26[16] But rise and stand upon your feet; for I have appeared to you for this purpose, to appoint you to serve and bear witness to the things in which you have seen me and to those in which I will appear to you,
Tit. 1[5] This is why I left you in Crete, that you might amend what was defective, and appoint elders in every town as I directed you,
Ex. 28[41] And you shall put them upon Aaron your brother, and upon his sons with him, and shall anoint them and ordain them and consecrate them, that they may serve me as priests.
Heb. 13 [17] Obey your leaders and submit to them; for they are keeping watch over your souls, as men who will have to give account. Let them do this joyfully, and not sadly, for that would be of no advantage to you.
Mt. 16 [19] I will give you the keys of the kingdom of heaven, and whatever you bind on earth shall be bound in heaven, and whatever you loose on earth shall be loosed in heaven."
Mt. 18 [18] Truly, I say to you, whatever you bind on earth shall be bound in heaven, and whatever you loose on earth shall be loosed in heaven.
Jn.[22] And when he had said this, he breathed on them, and said to them, “Receive the Holy Spirit. [23] If you forgive the sins of any, they are forgiven; if you retain the sins of any, they are retained.”
I think he would benefit from biblical arguments as would your brother. phil19034 is correct - the heart of Protestantism evolves around authority. That’s how you end up with 30 + thousand denominations.