“And there appeared unto them cloven tongues like as of fire, and it sat upon each of them.”
King James Version (KJV)
2:3 And there appeared distinct tongues, as of fire - That is, small flames of fire. This is all which the phrase, tongues of fire, means in the language of the seventy. Yet it might intimate God's touching their tongues as it were (together with their hearts) with Divine fire: his giving them such words as were active and penetrating, even as flaming fire.
Ac 2:3 There appeared unto them cloven tongues. Luminous tongues sat on each of them, "parting asunder" (Revised Version), or "distributing themselves" (margin). Meyer says that the idea is that they parted and distributed themselves on those present. These tongues symbolized the fact that the kingdom now inaugurated was to conquer by the spoken word, by the sword of the Spirit.