The central message of this sermon is that God's plan for salvation is not limited to individual conversions or even national Israel, but rather encompasses the entire nation and ultimately leads to their collective salvation. This revelation challenges the Gentile believers' tendency to be conceited about their place in God's kingdom, emphasizing instead the mysterious yet glorious nature of God's workings. The speaker argues that the partial hardening of Israel is temporary, tied to the full number of Gentiles coming into the church, after which all Israel will be saved. This means that every person of Jewish descent on earth at one time will have faith in Christ, resulting in a refined and purified remnant of Israel. The sermon encourages listeners to understand this mystery as part of God's overall plan for salvation, rather than trying to impose human interpretations or theological systems on it. Ultimately, the speaker wants his audience to grasp that God's ways are mysterious yet wondrous, and that His plan for all humanity is far greater than what can be comprehended by human understanding alone.