Matthew 3:11
NKJV - 11 I indeed baptize you with water unto repentance, but He who is coming after me is mightier than I, whose sandals I am not worthy to carry. He will baptize you with the Holy Spirit and fire.
For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
When I received the baptism of the Holy Ghost, I also received the baptism of fire at the same time. While speaking in tongues, the fire was churning in my bosom. The baptism of fire has given to me an exciting insight to the TRUTH and KNOWLEDGE of the Word of God. So the answer to the baptism of fire means a person has received a special gift from God to KNOW the TRUTH and receive KNOWLEDGE of the TRUTH of the Word of God.