When Did Paul Experience the Witness of the Spirit?

QUESTION: When did Paul receive the witness of the Spirit of adoption?

ANSWER: The first mention of the Holy Spirit in relation to him is in Acts 9:17, where Ananias declares the purpose of his mission to Saul, "that thou might be filled, with the Holy Spirit." The first offices of the Spirit to a penitent sinner trusting in Christ is to impart spiritual life and to witness his adoption into the family of God and to begin his sanctification by infusing the love of Christ. These are the blessings Saul received in Damascus. Some think he then and there received a full-fledged Christian character including entire sanctification ensphered in perfect love. But it is far more probable that this was a subsequent experience. Doubtless he advanced gradually from childhood to youth and, then to manhood in Christ. Entire sanctification requires a stronger faith than a penitent sinner can exercise, and, moreover, it is a gift for which he feels no special need, while overwhelmed with guilty fear in view of his past sins. In Gal. 1:15, 16, he speaks of two experiences, (1) called through his (God's) grace, and (2) the inward revelation of the Son, not to be confounded with the outward revelation of Christ in the sky, which blinded his eyes. This inward revelation could be made only to the inner eye purged from the film of sin as in the sixth beatitude, "Blessed are the pure in heart, for they shall see God." In John 14:21 to those who already love Christ, and to them only, does he promise to manifest himself. Only these can receive this wonderful manifestation. Probably Saul, while studying his three years' course in theology in Arabia, under the tuition of the Paraclete, became capable of receiving this inward revelation.

— Steele's Answers pp. 177, 178.