Kun () is an Arabic word for the act of "manifesting", "existing" or "being" andconsisting of the letters Kaph and Nun (letter). In the Qur'an, Allah commands the universe to "be" ("kun!" !), so that it is (fa-yakūnu ).
Kun fa-yakūnu has its reference in the Quran cited as a symbol or sign of God's mystical creative power. The verse is from the Quranic chapter, Surah Ya-Sin. The context in which the words kun fa-yakūnu appear in the 36th Chapter, verse number 82:
Does man not consider that We created him from a [mere] sperm-drop – then at once he is an open disputant? And he presents an (argument of) likeness for Us and forgets his own creation. He asks (in confusion): "Who will give life to the bones when they are disintegrated?" Say: "He will give life to them Who brought them into existence at first, and He is cognizant of all creation." He Who has made for you, from the green tree, fire. and then from it you kindle (fire). Is not He Who created the heavens and the earth able to create the like of them? Yes Indeed! and He is the Superb Creator (of all), the Ever-Knowing. Surely His Command, when He wills a thing, is only to say to it: Be! and it is!" Therefore glory be to Him in Whose hand is the Kingdom of all things, and to Him you shall be brought back.
The term also appears as part of 117th verse of the 2nd Quranic chapter, Surah Baqara.
(Allah,) The Originator of the heavens and the earth. When He decrees a matter, He only says to it, "be", and it is.
There are eight Quranic references to kun fa-yakūnu:
"She said: "O my Lord! How shall I have a son when no man hath touched me?" He said: "Even so: Allah createth what He willeth: When He hath decreed a plan, He but saith to it, 'Be', and it is!""[3:47]
"The similitude of Jesus before Allah is as that of Adam; He created him from dust, then said to him: "Be". And he was."[3:59]
"It is not befitting to (the majesty of) Allah that He should beget a son. Glory be to Him! when He determines a matter, He only says to it, "Be", and it is."[19:35]
"To Him is due the primal origin of the heavens and the earth: When He decreeth a matter, He saith to it: "Be", and it is."[2:116–117]
"It is He who created the heavens and the earth in true (proportions): the day He saith, "Be", behold! it is. His word is the truth. His will be the dominion the day the trumpet will be blown. He knoweth the unseen as well as that which is open. For He is the Wise, well acquainted (with all things)."[6:73]
"Verily, when He intends a thing, His Command is, "be", and it is!"[36:82]
"For to anything which We have willed, We but say the word, "Be", and it is."[16:40]
"It is He Who gives Life and Death; and when He decides upon an affair, He says to it, "Be", and it is."[40:68]