The first book and film both contain the information, from a note pinned to the cloak on Christmas Morning. I cannot remember if the book quote is the same word for word but in the film Harry receives the cloak with the following note:
Your father left this cloak in my possession before he died. It is time it was returned to you. Use it well.
The note was from Dumbledore.
ETA: I have just checked -- Dumbeldore's note is identical in the book and the film.
