“For the time has come for judgment to begin at the house of God; and if it begins with us first, what will be the end of those who do not obey the gospel of God?”
and if it begins with us first
The “if” of this phrase means that God assumes the reality that judgment begins first with the church.
God always begins with his people. Judgment always begins with God’s people. God is in the business of raising children for eternity. He expects us to be a credit to Christ on earth. Our Lord does not want his children to bring reproach on the Bible. He expects us to be an example to those without Christ and an asset to the cause of the gospel.
God will sovereignly intervene in our lives to bring us back to himself.
If we stand in the way of people coming to Christ, God will do something about that. We may be obstacles to our relatives and neighbors becoming Christians. It may be that some people who know us reject the gospel because of us. They see the irregularities and inconsistencies in our lives. They see that our talk outruns our walk and that we have more lip than life.