Acts 22
[16] And now why tarriest thou? arise, and be baptized, and wash away thy sins, calling on the name of the Lord.
We call upon the name of the Lord for the washing away of our sins when we are baptized.
The whole act of gospel conversion is visibly identified with and expressed in the act of baptism (Rom. 10:10). Ananias is simply calling on Saul to make a visible expression of his gospel conversion in baptism. In baptism the initial confession of faith is recounted and reaffirmed.
He had already previously acknowledged him as a born again child of God ("brother") as well as his divine calling to the ministry by God.
Later, when Paul recounts his own conversion experience he places it on the road to Damascus rather than in the act of baptism thus distinguishing the reality from the symbolic expression:
15 And I said, Who art thou, Lord? And he said, I am Jesus whom thou persecutest.
16 But rise, and stand upon thy feet: for I have
appeared unto thee for this purpose, to make thee a minister and a witness both of these things which
thou hast seen, and of those things in the which
I will appear unto thee; 17 Delivering thee from the people, and from the Gentiles, unto whom now I send thee,
18 To open their eyes, and to turn them from darkness to light, and from the power of Satan unto God, that they may receive forgiveness of sins, and inheritance among them which are sanctified by faith that is in me.
It is this very commission that Paul refers to in I Corinthians 1:17 where he says "Christ sent me not to baptize" but to preach the gospel.
It is this initial appearance that Paul refers to in Galatians 1:15-16:
But when it pleased God, who separated me from my mother’s womb, and called me by his grace,
16 To reveal his Son in me, that I might preach him among the heathen; immediately I conferred not with flesh and blood:
He is referring to the revelation of Christ WHEN he was called to preach by Christ. Acts 26:17 while standing on the road to Damascus Jesus says "NOW" I send thee. He was not called to preach by Christ in or after baptism. No, instead he IMMEDIATELY spent three days fasting and praying and only conferring with Christ BEFORE he was baptized.