New Defender's Study Bible Notes
2:2 filled all the house. The mighty wind, representing the coming of the Spirit, “filled all the house” the house; the baptism (i.e., “immersion”) by the Spirit thus was emphasized symbolically when the Lord Jesus first sent Him, fulfilling His promises (e.g., John 7:39; 14:16).
2:3 tongues like as of fire. These mysterious cloven tongues seem to depict a fiery root, divided into many individual tongues, enough to reach each person in the company. They were not real fire, however, but “like as of fire.” There have been various speculations as to their nature, but since it was a supernatural phenomenon, these seem pointless. In any case, the mighty wind filling the house and the fire-like tongues reaching each of the company are the audible and visible signs that the Holy Spirit had come, baptizing and filling all of them, fulfilling John the Baptist’s prophecy that Christ would baptize them “with the Holy Ghost and with fire” (Luke 3:16).