Application for other job

I am currently working as a COLLEGE ASSISTANT PROFESSOR a Govt aided College. Before joining this college I was working with another Private Christian Minority college. After joining the Govt aided college, due to my spiritual commitments and religious beliefs I have been visiting my former college and voluntarily took classes below 4 hours and did community work and everything was done without any CONTRACT and without any remuneration to my former college as I considered that as a free personal service to my former organisation. My present employer says why I didn't take permission from him and telling me he will sue me and take disciplinary action against me. But I have been going to the former college purely out of voluntary service and for doing community work.. Things have become so bad that I am mentally harassed every now and then and I want to quit this govt job to join anywhere else immediately.. Please suggest how can I do so and what to do if the Govt college do not provide an NOC or donot accept my resignation letter ans give a release letter