Albert Barnes Commentary Acts 18:6

"And when they opposed themselves and blasphemed, he shook out his raiment and said unto them, Your blood [be] upon your own heads; I am clean: from henceforth I will go unto the Gentiles." — Acts 18:6 (ASV)

And when they opposed themselves. To him and his message.

And blasphemed. See Barnes on Acts 13:4.

He shook his raiment. As an expressive act of shaking off the guilt of their condemnation. Compare Acts 13:45. He shook his raiment to show that he was resolved from now on to have nothing to do with them; perhaps, also, to express the fact that God would soon shake them off, or reject them. (Doddridge.)

Your blood, etc. The guilt of your destruction is your own. You only are the cause of the destruction that is coming upon you. See Barnes on Matthew 27:25.

I am clean. I am not to blame for your destruction. I have done my duty. The gospel had been fairly offered, and deliberately rejected; and Paul was not to blame for their ruin, which he saw was coming upon them.

I will go, etc. See Acts 13:46.