'Fast' in the Bible

I have known thy works, and where thou dost dwell -- where the throne of the Adversary is -- and thou dost hold fast my name, and thou didst not deny my faith, even in the days in which Antipas was my faithful witness, who was put to death beside you, where the Adversary doth dwell.

Lo, I come quickly, be holding fast that which thou hast, that no one may receive thy crown.