Heidelberg Catechism, Lord’s Day 11
[Can you be a Christian while believing in Jesus plus a bit of something else? No. "Either Jesus is not a perfect saviour," says Heidelberg, "or those who in true faith accept this saviour have in him all they need for their salvation." So if anyone looks for salvation in saints, themselves or anything else, rather than in Jesus alone, then they deny him. Jesus + Something = Nothing.]
Q29. Why is the Son of God called “Jesus,”
meaning “saviour”?
A29. Because he saves us from our sins,
and because salvation should not be sought
and cannot be found in anyone else.
Q30. Do those who look for
their salvation in saints,
in themselves, or elsewhere
really believe in the only saviour Jesus?
A30. No.
Although they boast of being his,
by their actions they deny
the only saviour, Jesus.
Either Jesus is not a perfect saviour,
or those who in true faith accept this saviour
have in him all they need for their salvation.