Being friends with the world will keep you from the kingdom. The Most High hates mixture so when you practice syncretism by mixing the clean with the unclean, such as mixing the Christian religion or any other religion with the things of the Most High you are defying His instructions.
4“Do not do so to יהוה your Elohim,
Deuteronomy 12
Whoever therefore intends to be a friend of the world makes himself an enemy of Elohim.
James 4
21“Not everyone who says to Me, ‘Master, Master,’ shall enter into the reign of the heavens, but he who is doing the desire of My Father in the heavens.
22“Many shall say to Me in that day, ‘Master, Master, have we not prophesied in Your Name, and cast out demons in Your Name, and done many mighty works in Your Name?’
23“And then I shall declare to them, ‘I never knew you, depart from Me, you who work lawlessness!’a
Matthew 7
10for Demas, having loved this present world, has deserted me
2 Timothy 4
23“And they are to teach My people the difference between the set-apart and the profane, and make them know what is unclean and clean.
Ezekiel 44