From Sahih Muslim (Hadith 6890):
Abu Huraira reported that Allah's Messenger (ﷺ) used to command us that as we go to our bedo, we should utter the words (as mention- ed above) and he also said (these words):" From the evil of every animal, Thou hast hold upon its forelock (Thou bast full control over it)
Reference: Muslim 6890