During their desert journey to the Promised Land, the Jews learned that God loved them in a special way, so that they could call themselves the "Chosen People". Deuteronomy reminds them that they were not chosen because they were a great nation. Rather, they were a tiny people. God chose them simply out of the immensity of divine love.
Paul's words to the Corinthians today are almost a paraphrase of God's words to Israel in Deuteronomy. The Corinthians are "among those called". God chose them. In themselves they were among those who "count for nothing": not influential, not well-born. Without Christ, they would have remained that way. But God was in Christ granting to them, and to us also, many great gifts: life, wisdom, sanctification, redemption.
Israel was called, not to privilege but to responsibility. They were not the exclusive owners of God's word and love. They were chosen to give God's word to humanity. They were chosen as part of God's plan of salvation. So too for the Corinthians and for ourselves. We are truly saved in Christ, but salvation is a gift that we must somehow share with others. Therefore we have nothing of our own to boast about. We may only boast "in the Lord".
Father in heaven, may we always be grateful companions of Jesus, and further Your love in this world.