There's an old poem, 'Even a man who is pure in heart and says his prayers by night may become a wolf when the wolfsbane blooms, and the autumn moon is bright'.
11 seconds sound clip from the The Wolf Man (1941) movie soundboard.
You can hear this line at 00:09:52.893 in the Blu-ray version of the movie.
Quote context
[...]
- It shows the wolf and the pentagram, the sign of the werewolf.
- That's a human being who, at certain times of the year, changes into a wolf.
- You mean, runs around on all fours, and bites and snaps and bays at the moon?
- Even worse than that, sometimes.
- What big eyes you have, Grandma.
- Little Red Riding Hood was a werewolf story. Of course, there have been many others.
- Yes, but what's this pentagram business?
- Every werewolf is marked with that, and sees it in the palm of his next victim's hand.
- Look, lady, if you're trying to scare me out of here, you're not getting very far.
- Please tell me, have you ever seen me before?
- Of course. How do you suppose I knew about the earrings?
- Tell you what we'll do. We'll take a little walk tonight and we'll talk it over.
- No.
[...]