Acts 22:12-16
12 And one Ananias, a devout man according to the law, having a good report of all the Jews which dwelt there,
13 Came unto me, and stood, and said unto me, Brother Saul, receive thy sight. And the same hour I looked up upon him.
14 And he said, The God of our fathers hath chosen thee, that thou shouldest know his will, and see that Just One, and shouldest hear the voice of his mouth.
15 For thou shalt be his witness unto all men of what thou hast seen and heard.
16 And now why tarriest thou? arise, and be baptized, and wash away thy sins, calling on the name of the Lord.
The Grace New Testament Commentary - Acts 22:16
22:16 The commencement of Paul's ministry awaited his baptism and, with it, the initiation of his fellowship with God (see comments at Acts 2:37-40). Paul as a classic personification of the nation of Israel had to likewise submit to water baptism as a condition for enjoying fellowship with God.
Accordingly Ananias concisely instructs Paul, "Arise and be baptized." Water baptism entailed a public identification with the very Lord Jesus whom Paul had previously persecuted. Paul's participation in baptism would "wash away (in the NT only here and 1 Cor 6:11) his sins" as a condition for, and thus the initiation of, fellowship with God.
Charles Bing - Grace, Salvation, and Discipleship - Be Baptized to Wash Away Sins, Acts 22:16
(Salvation) Interpretation: Paul was told he had to be baptized to have his sins washed away so that he could be saved.
(Discipleship) Interpretation: Paul was told that he had to be baptized to show his new identity in Christ and be forgiven of His former sins.
In this passage, the apostle Paul recounts his conversion on the Damascus Road to a crowd of people in Jerusalem. The result of his story is the same as the original narrative in chapter 9: Paul is saved. The difference is that this passage mentions baptism and calling on the name of the Lord for the washing away of sins.
It is clear from Luke's account in Acts 9 and in Paul's account in Acts 22 and 26 that Paul was saved at the time of his experience on the Damascus Road and not later. His own testimony in Galatians 1:11-12 is that he received the gospel directly from Jesus Christ, not Ananias. It is also critical to look at the timing in the account and its retelling. Paul called Jesus "Lord" after the revelation on the road. He says, "What shall I do, Lord?" which also indicates his submission to Christ's will. After the experience, the only instruction the Lord has for Paul concerns what he is now "to do" (Acts 22:10). In his retelling in chapter 22, Paul mentions several things Ananias did that indicate Paul is saved before his baptism: He calls Paul "brother," restores his sight, and relays God's commission for him to go to the Gentiles (Acts 22:13-15). So Ananias' command to "Arise and be baptized" is told to a saved Paul just as Jesus foretold to him that he would be told what to do (Acts 9:6).
The command to be baptized here is not then a condition for salvation, but as the text indicates, a condition for having sins washed away. The best explanation for this is to recall our discussion of Acts 2:38, where baptism is a way for Jews to show they are identifying with the Christian community and forsaking the generation of Jews who crucified the Messiah. Paul needs to be baptized to show his repentance for supporting the crucifixion of the Messiah and to have that sin forgiven (and perhaps also his sins of persecuting Christians and Christ, Acts 9:1, 5). "Calling on the name of the Lord" is not for salvation, but expresses an appeal for God's help, which Paul will need to fulfill his new ministry.
Again, we find a situation in Acts that is transitional in nature. The Jews of Jesus' generation shared in the sin of His crucifixion and received forgiveness for that sin only as it was confessed and forsaken in baptism. For the Jew, the Holy Spirit was given after salvation, as in Paul's case, while Gentiles received the Holy Spirit immediately upon believing in Christ and before baptism (Acts 10:43-44; 15:7-9).
It is important to see the transitional nature of the book of Acts and not view its events as normative for the church today. If we took Acts as the norm today, we would all speak in tongues (Acts 2:1-4; 19:1-6), sell all that we own and distribute it to the poor (Acts 2:45), meet in temples and homes (daily! Acts 2:46), have a morgue in the church basement for those who drop dead from lying in church (Acts 5:1-10), and receive the Holy Spirit subsequent to salvation. Our knowledge of the context rescues us from such conclusions.