Who said "I should have recognized him when I first saw him."?

This quote is attributed to Remus Lupin.

I should have recognized him when I first saw him. - Remus Lupin

"I should have recognized him when I first saw him."

Remus Lupin

Character in Harry Potter and the Prisoner of Azkaban

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"Dementors are among the foulest creatures that walk this earth."

"You're a true wizard, Harry."

"Understanding is the first step to acceptance."

"It is important to ask for help when you need it."