Is there a command to stop fire damage in minecraft?

If your players are burning, you can try:

• Whenever you trigger a teleport, send everyone into a room filled with water, before teleporting them to their proper destinations.

There's no specific command for it, but there is probably some commandblock contraption that can put the fire out.

Optional: give the player fire resistant (potion effect)

Players in creative lose the fire effect immediately after leaving fire. If you toggle the players you teleport into creative immediately, i.e. /gamemode 1 @a, then back to survival (/gamemode 0 @a) then the fire effects will go out.

There is a command that you can use or choose this setting when you make your Minecraft world: /gamerule fireDamage false. I use this command a lot when I do Survival Mode. It's really useful since fire can be really deadly sometimes.