Spirit-baptism is the engrafting by God the Holy Ghost, in association with water-baptism, into the New Testament Visible Church at her birth on Pentecost Sunday. It still recurs thereafter, in association with water baptism, whenever new Members are thereby engrafted into that Church Visible. Symbolically, it signifies and seals the regeneration of God's elect. See Westminster Confession of Faith 25:2b & 28:1b and Westminster Larger Catechism 62w, 161s, 162a, 165l, & 167pqy.
In Old Testament times, no Spirit-endued or Spirit-imbued person was thereby "baptized in the Spirit." All Old Testament predictions of Spirit-outpouring, were fulfilled only at Christ's own baptism — as consummated on Pentecost Sunday.
So too were all the water-baptisms administered by John the Baptist. He constantly preached to his Hebrew converts that Jesus, unto Whom he was baptizing, would Himself soon come — and baptize with the Holy Spirit and with fire! Lk. 3:16 cf. Acts 1:5 & 2:1f.
There were only three or four Post-Pentecost "out-tricklings" of the Spirit. Acts 8:12-18; 8:37?; 10:44f cf. 11:15f; & 19:1-6. These were all only in respect of gathering the 'first-fruits' of Non-Hebrew Christians — and ingrafting them into the new Church Visible alias Christ's storehouse for His wheat. Mt. 3:11f & Lk. 3:16f.
Soon after Acts 19:1-6, came Acts 19:9f. That was the final separation of the Spirit-completed Christ-professing Church from the Spirit-depleted Christ-denying Synagogue. Thenceforth, all Spirit-baptisms were at water-baptism — when new members were and are ingrafted into the Visible Church. Rom. 4:11,25; 6:3-5; I Cor. 1:2,14f; 3:6; 4:1; 6:11; 7:14; 10:2; 12:13; 15:29; 16:15; II Cor. 1:21f; Eph. 1:13f; 4:5,30; 5:26,32; 6:1-4; I Pet. 1:2; 3:18f; Rev. 7:4; 22:2. Details of much of the above now follow. * * * * * * * 1. There are many Old Testament examples of "Spirit-fallings" during those ancient days. Num. 11:25-26; 27:18; Judg. 3:10; 6:34; 11:29; 13:25; 14:6,19; I Sam. 10:10; 11:6; 10:10; 19:9,20,24; Ezek. 2:2; 3:12,14,24; 8:3; 11:1,24; etc. Such, however, are never called Spirit-baptisms! Indeed, the baptism of the Spirit at His future outpouring, is seen by the Old Testament as a single event — to occur at the incarnation of the Messiah and the sending forth of His Spirit. Ps. 72:6f; Prov. 1:23; Isa. 32:15f; 44:3f; Ezk. 36:25f; 39:7,29; Hos. 6:1-3; Joel 2:16,23,28f.
2. The water-baptisms of John the Baptist were always administered only: a) after professed repentance from sin and toward God-the-Father; b) together with the Word-proclamation of the need immediately to trust in the coming Messianic God-the-Son; and c) accompanied by the promise of His baptismal outpouring on Pentecost Sunday of God-the-Spirit. Mt. 3:1,11f; Mk. 1:4-8; Lk. 3:3-17; Jh. 1:15-34; 3:23-36. See too: Jh. 7:37-39; Lk. 24:49; Acts 1:4-5f,22f; 2:1-4; 10:37,44,47; 11:15-17; 13:23-25f; 15:8f.
3. Christ's own water-baptism was simultaneously a Spirit-baptism. Thereby His own human body was set apart as a temple of the Holy Spirit. Indeed, after His ascension and from Pentecost Sunday onward, the Visible Church would be His mystical body here on earth. Mt. 3:13-17; Mk. 1:9-12; Lk.
3:21-22; Acts 2:1-4,33-39,42-47; I Cor. 6:15-20; 12:13,27.
4. In Acts 2:1-4, all previously water-baptized people, being Hebrews, now received the completion of their water-baptism — in their Spirit-baptism into Christ's new earthly body (the Visible Church). As His wheat, they were then gathered into Christ's new storehouse. Gathered together were not only the twelve apostles who miraculously spoke forth the Gospel in foreign languages. Acts 1:2,8,11,26 & 2:1-4,7,14. Also there were the rest of the disciples, who did not then so speak. Acts 1:14-15 cf. Lk. 3:10-16. As Prof. Dr. F.F. Bruce declares in his Commentary on Acts 2:4, "the Spirit-baptism took place once for all, so far as the believing community was concerned."