if we are faithless, he will remain faithful, for he cannot disown himself.
...if we are unbelieving and unfaithful, Christ will remain true to his word, and we cannot hope to be saved...
If we believe not - Should we deny the faith and apostatize, he is the same, as true to his threatenings as to his promises; he cannot deny - act contrary to, himself.
True to his own nature, righteous character, and requirements, according to which he cannot accept as faithful one who has proved untrue to him. To do this would be to deny himself.