God of War Ragnarok has a tongue-in-cheek reference to an infamous line from the 2018 game that Kratos would say whenever he was set on fire.
Despite how much prestige 2018's God of War has, you might be surprised to find that Ragnarok manages to make fun of it quite a few times, and has quite a meta sense of humour. There are some obvious examples, such as the troll that Kratos kills in a cutscene very early in the game, but there are some other callbacks that only pop up in rare instances.
One of the times that Ragnarok will make fun of itself is when Kratos gets set on fire. In the 2018 game, if Kratos is set on fire during combat, Atreus will call out "Father, you're on fire!". Kratos will then nonchalantly say "it will pass" as if being set on fire is nothing but a minor inconvenience to him. In fairness, it basically is.
The line was quickly picked out by fans as being one of the funnier ones in the game, and a good example of Kratos' deadpan attitude adding to the game's humour. Well, that line's popularity has now been immortalised in God of War Ragnarok with a fun little callback that happens if you're set on fire again.
As you can see in the clip above (which has some mild mid-game spoilers), if Kratos is set on fire during combat, Mimir will call out to him, "You're on fire, Kratos", before smugly saying "it will pass". There's a certain knowing tone to how Mimir says the line that makes it clear that it's meant to be a callback to the last game.
It's just one example of Sony Santa Monica getting a little bit meta with itself and calling back to previous games in the series. It's a bit more unexpected in this case, as most of the references usually take place during boat rides and when walking between destinations, not combat.