Old Testament Holy Spirit

Question

I was reading a chapter on the Holy Spirit in the OT in Sinclair Ferguson's "The Holy Spirit", and at the end of this chapter he mentioned that God was circumcising the hearts of OT believers just as he does in the New Covenant. His text is Deuteronomy 30:6. Correct me if I'm wrong, but doesn't Deuteronomy 30:6 speak of that day when God would restore his people from their sin. Is this this not a look forward to the coming of Christ and the outpouring of God's Spirit at Pentecost?
Regardless of the answer to the question above, I am being slowly convinced of the Spirit's work in the Saints during the Old Covenant, but my question concerns Pentecost. One of the reasons I believed the Spirit only indwelt the faithful in the New Covenant, was because of Pentecost, and the outpouring of the Spirit that attended it. I reasoned that if Pentecost was the fulfillment of Deuteronomy 30:6, and Joel etc.., then how could this relationship have existed in the Old Covenant? What was special about Pentecost where the outpouring of the Spirit is concerned?

Answer

Actually, Deuteronomy 30:6 does not refer to the coming of Christ, though certainly Christ has a great deal to do with God's work in circumcising our hearts: it is God's love for us in Christ (expressed in election) that determines whether or not the Holy Spirit will regenerate us. The context of Deuteronomy 30 makes it clear that this blessing will pertain to the nation of Israel in Moses' day and after as the nation dwells in the Promised Land. "Circumcising" hearts simply refers to regeneration, and to the accompanying faithfulness to God that results from regeneration. It is the same thing that Ezekiel refers to as replacing the "heart of stone" with a "heart of flesh" (Ezek. 11:19; 36:26). Wherever there are believers, the Holy Spirit has done this work.

When the Holy Spirit was poured out at Pentecost, he was poured out on believers that he already had regenerated and indwelt. Pentecost was special because it marked a powerful outpowering of the Holy Spirit in charismatic gifting such as had never been seen before. Charismatic gifting by the Holy Spirit is quite distinct from his indwelling presence. All believers are indwelt in exactly the same way, but the Holy Spirit gifts whom and how he will (1 Cor. 12:4-7; Eph. 4:4,7). It was special because it was so pronounced and widespread. Such gifting had existed in the Old Testament, but never before in recorded biblical history had the Spirit gifted so many people so powerfully at the same time and in the same place. It was an astounding event intended to demonstrate forcefully the truth of the gospel they proclaimed. It was a gifting of the entire church with the power necessary to do the work of spreading the gospel to the world (Acts 1:4-5,8). At Pentecost, the Holy Spirit so gifted the church that they immediately began to gain far more disciples than Christ had ever won during his earthly ministry. What was different was not the way in which the Holy Spirit was manifested, but the power and scope of the manifestation.