'Once' in the Bible

My loved ones, while my thoughts were full of a letter which I was going to send you about our common salvation, it was necessary for me to send you one requesting you with all my heart to go on fighting strongly for the faith which has been given to the saints once and for ever.

Now it is my purpose to put you in mind, though you once had knowledge of all these things, of how the Lord, having taken a people safely out of Egypt, later sent destruction on those who had no faith;