Why was saul going to damascus?

Paul was originally travelling to Damascus in order to arrest and imprison the Christians there.

Acts 9 1And Saul [Paul], yet breathing out threatenings and slaughter against the disciples of the Lord, went unto the high priest, 2And desired of him letters to Damascus to the synagogues, that if he found any of this way, whether they were men or women, he might bring them bound unto Jerusalem.

Following his conversion, Paul was told to continue on to Damascus for a different reason - not only to receive his sight, but to receive the Holy Spirit and instructions for his new role: 17And Ananias went his way, and entered into the house; and putting his hands on him said, Brother Saul, the Lord, even Jesus, that appeared unto thee in the way as thou camest, hath sent me, that thou mightest receive thy sight, and be filled with the Holy Ghost. 18And immediately there fell from his eyes as it had been scales: and he received sight forthwith, and arose, and was baptized.