'Fast' in the Bible

Only let the lives you live be worthy of the Good News of the Christ, in order that, whether I come and see you or, being absent, only hear of you, I may know that you are standing fast in one spirit and with one mind, fighting shoulder to shoulder for the faith of the Good News.

The doctrines and the line of conduct which I taught you--both what you heard and what you saw in me-- hold fast to them; and God who gives peace will be with you.