'Disloyal' in the Bible

They profess to know God [to recognize and be acquainted with Him], but by their actions they deny and disown Him. They are detestable and disobedient and worthless for good work of any kind.

Come close to God [with a contrite heart] and He will come close to you. Wash your hands, you sinners; and purify your [unfaithful] hearts, you double-minded [people].

If anyone comes to you and does not bring this teaching [but diminishes or adds to the doctrine of Christ], do not receive or welcome him into your house, and do not give him a greeting or any encouragement;