See this passage explained in the notes on Acts 9:5, etc.

Whereupon as I went to Damascus - See the whole account of the conversion of Saul of Tarsus explained at large, in the notes on Acts 9:2 (note), etc.

Whereupon as I went to Damascus,.... Being intent, upon the above said things, to punish the saints, compel them to blaspheme, imprison them, and even put them to death on account of these things; upon this errand and business he went to Damascus, the chief city of Syria, where he knew there were many that believed in Christ, who had removed from Jerusalem thither, on account of the persecution, or were settled there before:

with authority and commission from the chief priests; the Jewish sanhedrim, to bring those of them at Damascus bound to Jerusalem, in order to be punished, as in Acts 9:2 and which the Ethiopic version adds here.

Whereupon (ἐν οἶς)

See on Acts 24:18. Better, on which errand; in which affairs of persecution.

Whereupon as I went to Damascus with authority and commission from the chief priests,

26:12-14 As I went to Damascus. Compare Ac 9:1-2. This is the third account of Paul's conversion, the first being in Ac 9:3-18, and the second in Ac 22:4-16. There are a few new details given here: (1) The over-powering glory of the Lord is specially dwelt upon here; (2) we are here told that the voice heard was in the Hebrew language (he was now speaking Greek to King Agrippa).

26:12 Acts 9:2.

26:12-23 Paul was made a Christian by Divine power; by a revelation of Christ both to him and in him; when in the full career of his sin. He was made a minister by Divine authority: the same Jesus who appeared to him in that glorious light, ordered him to preach the gospel to the Gentiles. A world that sits in darkness must be enlightened; those must be brought to know the things that belong to their everlasting peace, who are yet ignorant of them. A world that lies in wickedness must be sanctified and reformed; it is not enough for them to have their eyes opened, they must have their hearts renewed; not enough to be turned from darkness to light, but they must be turned from the power of Satan unto God. All who are turned from sin to God, are not only pardoned, but have a grant of a rich inheritance. The forgiveness of sins makes way for this. None can be happy who are not holy; and to be saints in heaven we must be first saints on earth. We are made holy, and saved by faith in Christ; by which we rely upon Christ as the Lord our Righteousness, and give up ourselves to him as the Lord our Ruler; by this we receive the remission of sins, the gift of the Holy Ghost, and eternal life. The cross of Christ was a stumbling-block to the Jews, and they were in a rage at Paul's preaching the fulfilling of the Old Testament predictions. Christ should be the first that should rise from the dead; the Head or principal One. Also, it was foretold by the prophets, that the Gentiles should be brought to the knowledge of God by the Messiah; and what in this could the Jews justly be displeased at? Thus the true convert can give a reason of his hope, and a good account of the change manifest in him. Yet for going about and calling on men thus to repent and to be converted, vast numbers have been blamed and persecuted.