Do not add to His words or He will reprove you and you will be proved a liar.
In order to not add to God’s words, you have to know His words.
I don’t think that this is only talking about those who blatantly add things to the Bible. Like those who change some wording around to make gay marriage or abortion ok. Or other religions like catholicism and mormonism that add their own books to the canon.
I think that this is a warning to take God’s words at face value, whether you like them or not. Some God-Loving people put words in God’s mouth because they don’t know what He actually said.
I’ve done it. I used to think that in some ways His word prevented woman from being in some types of leadership. Thankfully after studying with more clarity and guidance, I was proved a liar.
Just because today’s culture thinks sex outside of a heterosexual marriage is fine, doesn’t mean that it is. Yet many true Christians add to God’s words when they sleep around. Or in my case, just because some well meaning church leaders forbid women from serving as leaders doesn’t mean it’s right. This is adding to His words too.
The best thing any of us can do to live an authentic life with God is to learn His word, take it at face value, and do it.