In the early days of the Christian community, after the outpouring of the Holy Spirit, Christians - 'those who were of that Way', verse 2 - have been severely persecuted from Judaism since the stoning of Stephen. Acts 8. Paul / Saul, a young, gifted, fanatical Pharisee, also participates in this, authorized by the high priest and the High Council in Jerusalem. Saul 'breathes threats and murder'. He 'destroys the church' (8 verse 3), and thinks he is doing 'a service to God'. John 16 verse 2.
The persecution causes Christians to flee, including to Damascus. Saul asks the high priest for authority to persecute and capture them there too.
Near Damascus, a light suddenly shines around him, brighter than the sun. Saul and his companions fall to the ground. Jesus Christ Himself appears to him and addresses him in Hebrew: “Saul, Saul, why are you persecuting Me?”
“Who are you, Lord?”, “I am Jesus, whom you persecute; it is hard for you to turn your heels against the pricks.”
The last sentence refers to unwilling draft animals that back up against an iron pin. It marks Saul's resistance to God's work.
The church is the 'body of Christ', so Saul is persecuting Christ Himself.
The encounter with the exalted Christ brings about a deep change in Saul in one fell swoop. He tremblingly asks, “Lord, what do you want me to do?”
Blind, but with opened spiritual eyes, he is brought to Damascus. God sends the disciple Ananias to him.
In verse 15 of this chapter the Lord says about the Jew Saul:
“For he is a chosen instrument of mine, to bear my name before the Gentiles, and the kings, and the children of Israel.”
Acts 22 verse 14: 'And he (Ananias) said, The God of our fathers has predestined you to know His will, and to see the Righteous One, and to hear the voice of His mouth,
15 For you must be witnesses before Him before all men of what you have seen and heard."
In 1 Timothy 1 verse 15 Paul / Saul writes:
“This is a faithful saying and worthy of all acceptance, that Christ Jesus came into the world to save sinners, of whom I am chief.
16 But for this reason I have been shown mercy, so that Jesus Christ might show all His patience in me, the chief of sinners, as an example to those who would believe in Him to eternal life.”