'Fast' in the Bible

'I know where you live, where the throne of Satan [is]. And you hold fast to my name and did not deny your faith in me, even in the days of Antipas my faithful witness, who was killed among you, where Satan lives.

But I have a few [things] against you: that you have there those who hold fast to the teaching of Balaam, who taught Balak to put a stumbling block before the sons of Israel, to eat food sacrificed to idols and to commit sexual immorality.

So likewise you also have those who hold fast to the teaching of the Nicolaitans.

Nevertheless, hold fast to what you have until I come.

I am coming quickly! Hold fast to what you have, so that no one may take away your crown.