Boast only of the Lord
The wise man must not boast of his wisdom, nor the strong man of his strength, nor the rich man of his riches. What then is the right kind of boasting? What is the source of man’s greatness? Scripture says: The man who boasts must boast of this, that He knows and understands that I am the Lord. Here is man’s greatness, here is man’s glory and majesty: to know in truth what is great, to hold fast to it, and to seek glory from the Lord of glory. The Apostle tells us: The man who boasts must boast of the Lord.He has just said: Christ was appointed by God to be our wisdom, our righteousness, our sanctification, our redemption, so that, as it is written, a man who boasts must boast of the Lord.
Boasting of God is perfect and complete when we take no pride in our own righteousness but acknowledge that we are utterly lacking in true righteousness and have been made righteous only by faith in Christ.
Paul boasts of the fact that he holds his own righteousness in contempt and seeks the righteousness in faith that comes through Christ and is from God. He wants only to know Christ and the power of his resurrection and to have fellowship with his sufferings by taking on the likeness of his death, in the hope that somehow he may arrive at the resurrection of the dead.
Here we see all overweening pride laid low. Humanity, there is nothing left for you to boast of, for your boasting and hope lie in putting to death all that is your own and seeking the future life that is in Christ. Since we have its first fruits we are already in its midst, living entirely in the grace and gift of God.
It is God who is active within us, giving us both the will and the achievement, in accordance with his good purpose. Through his Spirit, God also reveals his wisdom in the plan he has preordained for our glory.
God gives power and strength in our labors. I have toiled harder than all the others, Paul says, but it is not I but the grace of God, which is with me.
God rescues us from dangers beyond all human expectation. We felt within ourselves that we had received the sentence of death, so that we might not trust ourselves but in God, who raises the dead; from so great a danger did he deliver us, and does deliver us; we hope in him, for he will deliver us again. (divineoffice.org)