I often get questions about this topic of whether the activity and presence of the Holy Spirit in the Old Testament age was the same or different than in our age. Some have worded it, “How has God’s activity among us really changed since Pentecost?” There are a number of ways to ask the same thing.
Here is a short article that answers that very difficult question in a way that is faithful to reconcile biblical passages that seem to indicate major differences, even though we know the Spirit was working in OT saints. I believe a thorough study of other passages would confirm this author’s conclusions. In the past I have described the transition in the Spirit’s activity at Pentecost as “different in degree, but of the same kind.” Here is how this author states his conclusion.
Both the OT and NT present the Holy Spirit as the only regenerating agent in the plan of redemption, the sole agent of sanctification—working in the hearts of OT and NT believers, convicting them of sin and producing genuine God worshippers—and as the only agent of empowerment, enabling the saints of both testaments to live holy lives which are acceptable to God. He continues to fulfill this role in us today as He had done from the beginning of time. The extent of His work in believers has increased, but He was always in believers and among believers.
Click on the link above to read the whole article. I think it will help you if you desire to have a clearer understanding of this issue.