They are waiting to talk to Saint Peter outside the gates of Heaven.
Saint Peter: “Sisters, confess your sins and you may enter paradise.”
Nun #1: “Saint Peter, forgive me, in my life I once gazed lustfully at a man’s penis.”
St Pete: “Sister, rinse your eyes with this Holy Water and then you may enter they Kingdom of Heaven.”
Nun #2: “Saint Peter, forgive me, I once touched a man’s penis.”
Petey: “Sister, wash you hands in this Holy Water and then you may enter the Kingdom of Heaven.”
Nun #4: *taps Nun #3 on the shoulder and says* “Do mind if I gargle with that water before you sit in it?”
Idk if this was an old one, but it’s good.