J.k. Rowling said this quote
“ Oh, for heaven’s sake, Sirius, Dumbledore said no!”A bearlike black dog had appeared at Harry’s side as Harry clambered over the various trunks cluttering the hall to get to Mrs. Weasley.“Oh honestly,” said Mrs. Weasley despairingly. “Well, on your own head be it!”The great black dog gave a joyful bark and gamboled around them, snapping at pigeons, and chasing its own tail. Harry couldn’t help laughing. Sirius had been trapped inside for a very long time. ”