baptism of fire

noun4

1. •
   The gift of the Holy Spirit.
2. •
   (figurative) The first experience of a severe ordeal, especially a first experience of military combat

   • Having to deal with a bomb scare on his first day was a real baptism of fire for John.
3. •
   Tribulation endured as spiritual discipline.

   • And the Father's counselor suggested that he invite you along to help: sort of a re–baptism of fire, so to speak. — 2013
4. •
   Martyrdom by immolation.