Once the Jews in the synagogue at Corinth opposed Paul, and Paul separated himself from them, he began to preach daily next door in the home of Gaius Titius Justus (Acts 18:7). Whether the Jewish party opposed God and blasphemed the way or opposed God by simply opposing and insulting Paul, they placed themselves under the judgment of God (cp. Romans 13:2), and when this occurs God tells us to separate ourselves from those people in order to avoid partaking in judgment with them (cp. Revelation 18:4). Therefore, Paul broke off fellowship with the synagogue, saying he was innocent of the path they had chosen, and their blood was upon their own heads (Acts 18:6).
The principle upon which Paul was acting is found in ancient Jewish custom (2Samuel 1:16; 1Kings 2:31-33; cp. Matthew 27:25 and Acts 5:28). Here Paul was expressing himself as the faithful watchman of Ezekiel 33:1-9 in the tradition of this ancient Jewish custom. The implication of the prophecy is that judgment is coming whether or not the watchman blows the trumpet warning and whether or not the people heed the warning. The consequences are certainly different for both. If Paul didn’t preach to the Jews and simply took his message to the gentiles, the blood of the Jews would be upon Paul’s head. Paul claims, because he did warn them, he was innocent of God’s coming judgment upon them.
On the other hand, had the Jews heeded Paul’s message, judgment would have come, but they would have saved their lives by turning to the God through the Gospel. In other words, God would have judged them innocent. They rejected Paul’s prophetic claim that the judgment of God was coming upon them, and history grimly records the result in the loss of their nation. The whole idea expressed here—your blood be upon your own heads—presumes judgment and this presumes Jesus has become Judge over the Jews and the rest of the world (cp. 1Corinthians 15:25, 28), and this is expressed in Jesus’ own statement in Matthew 28:18, namely “All authority in heaven and on earth has been given to me!”
Paul is not the only apostle who proclaimed that the judgment of God would begin in the 1st century. Peter also wrote that the time of God’s judgment was to begin then in their lifetimes. Notice:
For it is time for judgment to begin, starting with the house of God. And if it starts with us, what will be the fate of those who are disobedient to the gospel of God? (1Peter 4:17 NET.)
From this point on Paul claimed he wouldn’t preach in their place of worship, but would go to the gentiles. And, veiled in this statement is another prophecy of judgment. The Jews, from Abraham to the 1st century lived in a close relationship with God in covenant with him and that relationship was about to pass under his judgment. Nevertheless, the gentiles who lived afar off from God were now called, through the Gospel, into a covenant with him and in so doing to enjoy a closer relationship with their God. This, too, as in the matter of the Jews before them, would eventually pass through the judgment of God’s appointed Ruler, Jesus, and all who heed the prophetic message will save their lives, but those who do not will eventually incur the wrath of the Judge of all—Jesus, the King and Judge, in whom God has invested all the authority of heaven and earth (Matthew 28:18).