The idiom playing with fire means engaging in risky behavior. It’s a warning about actions that could get you into trouble, just like recklessly playing with fire can lead to a sudden blaze. To play with fire is to take actions or make decisions that have a high probability of causing negative or harmful repercussions. It suggests that someone’s either unaware of or is ignoring the potential dangers of their current decision-making. The origin of “playing with fire” as an expression is not precisely documented, but the metaphorical use of fire to signify danger, temptation, or risk is ancient and widespread across cultures. Fire has always been both a useful tool and a potential danger to humans. It’s no surprise that it’s morphed into such a visual note of caution.

Source: Grammarist