'Unstable' in the Bible

They have eyes full of adultery, constantly looking for sin, enticing and luring away unstable souls. Having hearts trained in greed, [they are] children of a curse.

speaking about these things as he does in all of his letters. In which there are some things that are difficult to understand, which the untaught and unstable [who have fallen into error] twist and misinterpret, just as they do the rest of the Scriptures, to their own destruction.