Boyd’s Bible Dictionary:

Symbol of God’s presence
(Gen. 4:4-5; 15:17; Ex. 3:2; Judg. 13:19-20). Worshipped (2 Kings 17:17); punishment (Lev. 20:14; 21:9). Christ comes in (2 Thess. 1:8). World destroyed by (2 Pet. 3:7).

Concise Bible Dictionary:

God was early revealed in fire. The searching character of His righteous judgment was thus set forth, whether in the acceptance of good or the condemnation of evil. When Moses at Horeb approached the burning bush he was cautioned not to draw near, but to remove his shoes, for the ground was holy. God spake to him out of the burning bush (Ex. 3:1-6). On Mount Sinai "the sight of the glory of the. Lord was like devouring fire" (Gen. 24:17). Moses declared to Israel, "The Lord thy God is a consuming fire" (Deut. 4:24). When Aaron began his ministrations in the tabernacle fire came out "from before the Lord, and consumed upon the altar the burnt offering and the fat" (Lev. 9:24: Compare 1 Kings 18:38; 1 Chron. 21:26; 2 Chron. 7:1-3). Nadab and Abihu offered “strange fire,” and fire went out from the Lord and consumed them (Lev. 10:1-2). Thus God manifested Himself in fire to Moses. He showed His acceptance of the sacrifices by fire from heaven; He vindicated His servant Elijah, when he stood alone against the prophets of Baal, by consuming the sacrifice, the wood and the stone, by fire from heaven (1 Kings 18:38); and He vindicated His own honor by fire, by destroying those who were disobedient in approaching to Him. The general idea in “fire” is that of judgment.
In the N. T. it is repeated, "Our God is a consuming fire" (Heb. 12:29), to consume the dross in the Christian, as gold is tried and purified in the fire; and to judge and punish the wicked with unquenchable fire; who are also described as being Baptized WITH FIRE (Matt. 3:11-12). One of the most awful things connected with this word is the description of the place of eternal punishment as THE LAKE OF FIRE (Rev. 19:20; Rev. 20:10, 14-15). What mercy to be delivered therefrom!