PETER: Her light is growing faint, and if it goes out, that means she is dead! Her voice is so low I can scarcely tell what she is saying. She says — she says she thinks she could get well again if children believed in fairies!
(He rises and throws out his arms he knows not to whom, perhaps to the boys and girls of whom he is not one.)
Do you believe in fairies? Say quick that you believe! If you believe, clap your hands!
(Many clap, some don’t, a few hiss. Then perhaps there is a rush of Nanas to the nurseries to see what on earth is happening. But TINK is saved.)
Oh, thank you, thank you, thank you! And now to rescue Wendy!
(TINK is already as merry and impudent as a grig, with not a thought for those who have saved her.

J. M. Barrie (1860-1937) Scottish novelist and dramatist [James Matthew Barrie]

Peter Pan, Act 4 (1904, pub. 1928)
    (Source)

In Barrie's 1911 novelization, Peter and Wendy, ch. 13 "Do You Believe in Fairies?" this is rendered:

Every moment her light was growing fainter; and he knew that if it went out she would be no more. She liked his tears so much that she put out her beautiful finger and let them run over it. Her voice was so low that at first he could not make out what she said. Then he made it out. She was saying that she thought she could get well again if children believed in fairies.
Peter flung out his arms. There were no children there, and it was night time; but he addressed all who might be dreaming of the Neverland, and who were therefore nearer to him than you think: boys and girls in their nighties, and naked papooses in their baskets hung from trees.
“Do you believe?” he cried.
Tink sat up in bed almost briskly to listen to her fate.
She fancied she heard answers in the affirmative, and then again she wasn’t sure.
“What do you think?” she asked Peter.
“If you believe,” he shouted to them, “clap your hands; don’t let Tink die.”
Many clapped.
Some didn’t.
A few little beasts hissed.
The clapping stopped suddenly; as if countless mothers had rushed to their nurseries to see what on earth was happening; but already Tink was saved. First her voice grew strong, then she popped out of bed, then she was flashing through the room more merry and impudent than ever. She never thought of thanking those who believed, but she would have liked to get at the ones who had hissed.