Let the one who boasts boast in the Lord
The Old Testament
“But let him who boasts boast in this, that he understands and knows Me, that I am the LORD, who exercises loving devotion, justice and righteousness on the earth— for I delight in these things,” declares the LORD.
Jeremiah 9:24
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In the New Testament
Therefore, as it is written: “Let him who boasts boast in the Lord.”
1 Corinthians 1:31
BSB
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Read the full text (4 verses)
Let not the wise boast in their wisdom, nor the strong in their strength, nor the rich in their riches. Let the one who boasts boast in this: that he understands and knows me, the LORD. And in Isaiah: who has fathomed the Spirit of the LORD, or taught him as his counsellor?
Paul uses both texts in one argument. Christ is made unto us wisdom, righteousness, sanctification and redemption; therefore, he that glorieth, let him glory in the Lord, and from the context it is clear he means Christ. A few sentences later he quotes Isaiah: who hath known the mind of the Lord? And he answers: we have the mind of Christ. Where Isaiah says nobody knows God's mind, Paul says: in Christ it has been made known.