‘But the Lord said to him, “Go your way, for he is a chosen vessel to me, to bear my name before the Gentiles and kings, and the children of Israel, for I will show him how many things he must suffer for my name's sake.” '
The Lord patiently makes it clear that He is aware of all the circumstances, but that nevertheless He has chosen Saul as one who in His Name will go to the Gentiles and before kings as well as to the children of Israel where he will suffer for His name's sake. Lying behind this description are God's words to the Servant in Isaiah in Isaiah 49:6-7 also partly cited in Acts 13:47. There also Gentiles, kings and Israel are mentioned. Like the church he is to become one with God's chosen Servant in fulfilling this responsibility. But it is also a summary of Paul's future. Note that unusually the witness to the Gentiles comes before that to Israel. The burden of his life is being represented. He is primarily to be the Apostle to the Gentiles, even though he will also go to the children of Israel. The witness before kings will come out later in Acts. And then, both included in this and following this, he must suffer greatly for Christ's sake.