Use the /ignite command to set entities on fire and the /extinguish command to put them out.
Adds a new /ignite and /extinguish commands to the game that sets targeted entities on fire or puts them out.
Command Examples:
/ignite ignites the player who used the command for 10 seconds/extinguish extinguishes the player who used the command/ignite @a ignites all players/extinguish @a extinguishes all players/ignite Steve 25 ignites Steve for 25 seconds/extinguish Steve extinguishes SteveThis command requires a permission level of 2 (Operator)