เศาะฮีห์อัล-บุคอรี #95
Sahih (Authentic)
Whenever the Prophet (ﷺ) spoke a sentence (said a thing), he used to repeat it thrice so that the people could understand it properly from him and whenever he asked permission to enter, (he knocked the door) thrice with greeting
สายรายงาน (อิสนาด)
Narrated Anas