'Keep Your Hearts' in the Bible

Then take care that you keep your hearts true to the Lord, who took you out of the land of Egypt, out of the prison-house.

And the peace of God, which passeth all understanding, shall keep your hearts and minds through Christ Jesus.

As for you, the Spirit which he gave you is still in you, and you have no need of any teacher; but as his Spirit gives you teaching about all things, and is true and not false, so keep your hearts in him, through the teaching which he has given you.

And now, my children, keep your hearts in him; so that at his revelation, we may have no fear or shame before him at his coming.