What the Bible says about God's Treasure
(From Forerunner Commentary)
The idea here is similar to the Parable of the Hidden Treasure. God has a treasure—us—and He hides it in Christ. We are part of the body of Christ. We are hidden in it like in a vault, a treasure house, a place to keep valuables securely and safely, where they will not be stolen or in any way degraded.
If we are truly seeking those things which are above, and we are truly "in Christ," then our eternal life is secure. This is not the Protestant doctrine of eternal security, which is false. Protestant theologians teach that once one believes in Christ, that is it—one's eternal life is guaranteed without any further effort. In verse 1, however, Paul makes it clear that we must be doing something—seeking heavenly things—for this to happen.
Richard T. Ritenbaugh
Parables of Matthew 13 (Part 3): Hidden Treasure