Going To A Church Can Be Sinful
Yes it is a sin to fellowship with sinners wilfully as you gather together with them. In the world many will argue against this, arguing against God for their local (government instituted) "church". Saying their family church is not like this or that making excuses for each point brought up. Never minding that there is another building they would consider "Christian" just down the road from theirs which has different doctrine they teach, Mathew 7:13-14 states there is only one straight and narrow for a Christian.
Just because something is accepted doesn't make it right (Luke 16:15). Just because pot it legal doesn't make it right (*1 Thessalonians 5:22*). And just because someone says a thing is of God does not make it from God (Romans 3:4). These churches across the breadth of the earth are giving way to sin while pretending to be a "house of God", it is all a bunch of lies and falsehoods just as Israel had when they transgressed. Why do the people imagine a vain thing (Psalm 2:1).
Amos 4:4-5 KJV Come to Bethel, and transgress; at Gilgal multiply transgression; and bring your sacrifices every morning, and your tithes after three years: (5) And offer a sacrifice of thanksgiving with leaven, and proclaim and publish the free offerings: for this liketh you, O ye children of Israel, saith the Lord GOD.
There are much more verses to this topic then what can be expressed in one thread. In the video below you will hear of some scriptures on the matter. May it be edifying for you to have a better understand according to the word of God, not just following after the traditions of men. They are puffed up in their fleshly minds and against God, no matter how good they can make something sound. (Colossians 2:8 & 18-22).
