This is an unhappy expression, bringing in the name of God where it does not occur. In the O.T. it is chalilah, 'far be it.' Ge 44:7,17, etc. In the N.T. ?? ???????, 'let it not be.' Ro 3:4,6,31, etc.
Never! Let God be true to his word, though every man be perfidious ??as it is written, That thou mayest be vindicated in thy pleadings, and triumph in thy trial.
Never! In that case, how could he judge the world?
Then 'by this faith' we 'cancel the Law'? Not for one moment! We uphold the Law.