'Understand' in the Bible

So understand that it is the people who live by faith [with confidence in the power and goodness of God] who are [the true] sons of Abraham.

But at that time, when you did not know [the true] God and were unacquainted with Him, you [Gentiles] were slaves to those [pagan] things which by [their very] nature were not and could not be gods at all.

Now, however, since you have come to know [the true] God [through personal experience], or rather to be known by God, how is it that you are turning back again to the weak and worthless elemental principles [of religions and philosophies], to which you want to be enslaved all over again?