“But it is equally important to observe that that religion which Jesus had was not Christianity. Christianity is a way of getting rid of sin, and Jesus was without sin. His religion was a religion of Paradise, not a religion of sinful humanity. It was a religion to which we may perhaps in some sort attain in heaven, when the process of our purification is complete (though even then the memory of redemption will never leave us); but certainly it is not a religion with which we can begin. The religion of Jesus was a religion of untroubled sonship; Christianity is a religion of the attainment of sonship by the redeeming work of Christ.”
This is from Machen’s book, Christianity and Liberalism, a book I cannot recommend more highly. I have read it several times and still refresh myself revisits. His basic thesis is that liberal Christianity is not Christianity but another religion. I believe that to be true.