Ethics: Are Beliefs Ever Sins?

We know that having an abortion is almost always a sin, but what if a person doesn’t have one and merely believes it’s okay to do so? Is it a sin to deny the resurrection or to believe that Adam and Eve weren’t real people? What if someone believes that spanking children is sinful? On the one hand, it seems that some erroneous beliefs must be sins since otherwise there isn’t any consequence to failing to love God with our minds. This would seem to fit with the idea that certain doctrines are held as necessary for having a proper relationship with God. It wouldn’t make much sense to say that you have to believe the Trinity to be a Christian but that it’s not a sin to deny the Trinity. But on the other hand, does God ever judge you for your beliefs, even if they don’t show up as behaviors? Are there some wrong beliefs which are more objectionable than actual sinful behaviors? Also, aren’t we all wrong about some of our beliefs? Did Jesus’s sacrifice pay for the sins of the mind, if there are any? And what if a person is shown the truth but refuses to believe it? To what extent might that be a sin?