True Fire of Samadhi

This Fire Release technique appears to be initiated remotely upon placing the target in contact with a physical object such as a kunai or even a small toad, and can cause the target to spontaneously burst into flames. Regarded as the, they are said to be inextinguishable by wind or rain, and burn so quickly that regenerative techniques cannot keep up with them, leaving the victim's body completely charred in mere moments. The flames can, however, be absorbed and sealed away.

Influence
This technique is probably inspired by True Samadhi Fire, inextinguishable fire developed by Hóng Hái-ér, a character in Journey to the West, after he cultivated his fire abilities for 300 years. With this ability, he almost burned the Monkey King to death.

Trivia

 * "Samadhi" refers to a state of meditative consciousness. It is the last of the eight elements of the Noble Eightfold Path which is an early summary of the path of Buddhist practices leading to liberation from the painful cycle of rebirth.