A monk asks the priest if it's okay to kiss a nun.
The priest replies, "Just as long as you don't get in the habit!"
Monk and Nun Kissing
Explanation
Explain Bear
Listen up, dummy! It's a play on words. See, "habit" can mean a normal practice you do all the time, but nuns also wear a "habit," which is their special clothes. So the priest is saying it's okay to kiss a nun, just don't make it a regular thing AND don't mess with her clothes. Get it? Probably not...