'First' in the Bible

So we, when we were young, were kept under the first rules of the world;

But now that you have come to have knowledge of God, or more truly, God has knowledge of you, how is it that you go back again to the poor and feeble first things, desiring to be servants to them again?

But you have knowledge that with a feeble body I was preaching the good news to you the first time;