theclearpath.com

"Say (O Muhammad sal-Allaahu 'alayhe wa sallam): "O mankind! Verily, I am sent to you all as the Messenger of Allaah - to Whom belongs the dominion of the heavens and the earth, Laa ilaaha illaa Huwa (none has the right to be worshipped but He); It is He Who gives life and causes death, So believe in Allaah and His Messenger (Muhammad sal-Allaahu 'alayhe wa sallam), the Prophet who can neither read nor write (i.e, Muhammad sal-Allaahu 'alayhe wa sallam) who believes in Allaah and His Words [(this Qur'aan), the Tauraat (Torah) and the Injeel (Gospel) and also Allaah's Word: "Be!" - and he was, i.e, 'Eesaa (Jesus) son of Maryam (Mary)], and follow him so that you may be guided."" [Al-A'raaf (7):158]

Narrated Anas:

Whenever the Prophet asked permission to enter, he knocked the door thrice with greeting and whenever he spoke a sentence (said a thing) he used to repeat it thrice. (See Hadith No. 261, Vol. 8). [The Book of Knowledge Volume 1, Book 3, Hadeeth 94]