Can I ask my current employer for a reference if i'm not quitting?

Hi everyone!

I know people typically do not ask their current managers/boss to be a reference for a new job they're seeking out, but is it okay if I'm not intending on leaving my current one? Im applying for a casual position that's going to be weekends only. My current job is a M-F 9-5 type deal so they would never get in the way of one another. In this case, would it be appropriate to ask my current employer?

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