12: 49 What is the fire that Jesus came to send on the earth?

Jesus uses fire here figuratively of the Holy Spirit's empowering of believers to proclaim the gospel (cp Mt 3:11-13; Mk 1:6-9; Lk 3:16; Ac 1:1-8; 2:1-4).

Jesus longed for the gospel to be proclaimed throughout the earth but He had to die first in order for the Holy Spirit to come and empower believers for service (cp Lk 12:50 with Jn 12:23-24; 16:7-15; Lk 24:49 and Ac 1:1-8).

Jesus' death and resurrection removed the restraints on the outpouring of the Holy Spirit and the gospel being proclaimed throughout the earth, but Jesus also knew that the proclamation of the gospel would cause much division and strife, even pitting family members against each other (cp Mt 10:34-36; Mk 10:29-30; Lk 12:51-53).

Jesus is not the cause of division, but the occasion of it. The division is caused by the rebellion of men against the Gospel (cp 1Cor 1:18, 23; 2Cor 2:15-16).