Charles Spurgeon Commentary Acts 22:13-14

"came unto me, and standing by me said unto me, Brother Saul, receive thy sight. And in that very hour I looked up on him. And he said, The God of our fathers hath appointed thee to know his will, and to see the Righteous One, and to hear a voice from his mouth." — Acts 22:13-14 (ASV)

If Paul was to be an apostle, it was necessary for him to see the Lord Christ, for one of the qualifications of an apostle was that he should be able to bear witness, from his eyesight and from his hearing, to the existence of the Lord Jesus Christ. Therefore, Saul did, at that time, see that Just One, and did hear the voice of his mouth.