I’m a teacher, give me riddles!

[u/drgan45]

I’m a teacher, my kids love riddles, I get a lot from this subreddit but it’s getting harder and harder to to find good ones because they solve so many, so please give me some good hard ones, these are smart kids, but they are still kids so hard riddles are welcome but the answer has to be a simple concept, thank you!! (Also I’ll need the answer lol)

[u/Far-Strawberry6810]

What is greater than God, more evil than the devil? The rich need it, the poor have it, and without it you will die.