"To me, though I am the very least of all the saints, this grace was given, to preach to the Gentiles the unsearchable riches of Christ..." (Ephesians 3:8 ESV)
"...that their hearts may be encouraged, being knit together in love, to reach all the riches of full assurance of understanding and the knowledge of God's mystery, which is Christ, in whom are hidden all the treasures of wisdom and knowledge." (Colossians 2:2-3 ESV)
Jeremy Walker writes...
Who can appreciate the wonder of the good news in Christ Jesus? Who has exhausted those precious promises? Who has understood all those shining certainties which are “Yes” and “Amen” in Christ to the glory of God, this revelation of life abundant that Christ has brought in and with Himself (2 Cor. 1:20)
Paul has recorded in scant outline in this letter to the Ephesians only some of the unsearchable riches of Christ. He is scratching the surface, picking up a few of the diamonds that lie in the topsoil. He could speak of the riches of Christ’s righteousness, compassion, goodness, and on and on. The apostle says that none of them can properly be fathomed. No one has ever walked through these fields, climbed these mountains, traversed these valleys; no one has ever explored these trackless seas to their depths and extents, traced the rushing rivers to their source—the Lord Jesus Christ is in Himself a whole world of wonder!
However much you think you know these things, they remain unexhausted and inexhaustible. You have barely started to know them. They are so vast that you cannot reach the end of them. They are so intricate that no matter how you trace them with the fingers of your most incisive thoughts, no matter how carefully you discern the beauty and wisdom of these works of God, you will never be able to come to the end or be able to put it all together. You must stand back and gaze again at the tapestry of God’s saving works through Christ Jesus and say, “These things are beyond searching out. Here I bow, defeated and adoring.” If you had a thousand lifetimes, you would need a thousand, thousand more even to begin to understand these things. Only eternity will give you time enough to start searching out more of the unsearchable riches of Christ.
But what every saint must grasp—what we long for all people to grasp—is that these unsearchable riches are all found in Christ... Here we find true deity (He is God) and true humanity (He becomes man) in true agony—suffering to purchase our redemption blessings.
You cannot know these blessings apart from Jesus Christ or find them other than in Him. You cannot experience them until you are in Christ. You cannot receive them without Him, because these are the unsearchable riches of Christ, belonging to and found in Him alone. As we have said, He is both treasury and treasure. You cannot open the box, take out the treasures, and walk away with them. They belong in the display cabinet and are splendid in themselves. In the abstract, love, forgiveness, truth, power, hope, and mercy are beautiful and good in themselves and can be great things. But it is when they are found in and of Christ that they are constituted unsearchable, and being of Christ, they are for salvation. To be found in Him is to come into possession of them. Because they belong to Him and are found in Him, they stretch beyond human comprehension. It is because they are of Him and in Him—our Ransomer—that they are given for human blessing.
The unsearchable riches of Christ are proclaimed in order that they might be known and enjoyed, received by sinners who have come to rest in the boundless resources of Jesus Christ as their Deliverer, the One given for the very purpose of meeting the needs of fallen people.
Grasping our new identity as those possessed of this Christ in all His matchless beauty and glory is vital to living in accordance with that new identity. As these things are given to be received, so they are given to be pondered and enjoyed: “For all things are yours: whether Paul or Apollos or Cephas, or the world or life or death, or things present or things to come—all are yours. And you are Christ’s, and Christ is God’s” (1 Cor. 3:21–23).
(Jeremy Walker, Life in Christ: Becoming and Being a Disciple of the Lord Jesus Christ)