Religion can be biblically decribed as the act of worshipping God or other gods. The worship of the almighty God Jehovah is the trule religion and according to the book of john, we must worship God in spirit and in truth. This is because God is spirit and so we must worship in spirit and with honesty.
James 1 verse 26 cautions belivers in Christ to control what they say and be wary of how they speak lest they speak false or against another person. He says that a man who says he worships almighty God but does not control what utterances he makes is practicing a vain religion.
The book of 1st Timothy 3 verse 15 refers to the house of God as the church of the living God and also the pillar amd the ground of the truth. This tells us that the worship of the almighty God is the true religion.
Remain Blessed !