This is a reference to those who have rejected the good news of God’s gracious gift to humanity in the sending of his only Son (recall Colossians 1:6, Colossians 1:23). By their actions such people have provoked the Lord’s anger and so attracted his righteous judgment in the damnation of hell.
17 For it is time for judgment to begin at the household of God; and if it begins with us, what will be the outcome for those who do not obey the gospel of God?