'Once' in the Bible

Beloved, while I was making every effort to write you about our common salvation, I was compelled to write to you [urgently] appealing that you fight strenuously for [the defense of] the faith which was once for all handed down to the saints [the faith that is the sum of Christian belief that was given verbally to believers].

Now I want to remind you, although you are fully informed once for all, that the Lord, after saving a people out of the land of Egypt, subsequently destroyed those who did not believe [who refused to trust and obey and rely on Him].