She said: "O my Lord! How shall I have a son when no man has touched me." He said: "So (it will be) for Allah creates what He wills. When He has decreed something, He says to it only: “Be!” and it is. S. 3:47
She said: "How can I have a son, when no man has touched me, nor am I unchaste?" He said: “So (it will be), your Lord said: 'That is easy for Me (Allah): And (We wish) to appoint him as a sign to mankind and a mercy from Us (Allah), and it is a matter (already) decreed, (by Allah).’” S. 19:20-21
Same account with additions. Why did Allah need to repeat the same annunciation story, adding to it things that he did not mention previously, like “nor am I unchaste” and the rest? remember, we are talking about one author here, not many authors as in the NT where repetations and varying details is something normal since more than one person are writing.
Check as well 20:9-24, 27:7-14, 28:29-33
Has the story of Moses Reached Thee? Behold he saw a fire: So he said to his family, "Tarry ye: I perceive a fire; perhaps I can Bring you some burning brand Therefrom, or find some guidance At the fire." But when he came to the fire, a voice Was heard: "O Moses! "Verily I am thy Lord! Therefore (in My presence) Put off thy shoes: thou art In the sacred valley Tuwa. "I have chosen thee: Listen, then, to the inspiration (Sent to thee). “Verily, I am God: There is no god but I: So serve thou Me (only), And establish regular prayer For celebrating My praise. Verily the hour is coming- My design is to keep it Hidden- for every soul To its reward By the measure of its endeavor. Therefore let not such as Believe not therein But follow their own Lusts, divert thee therefrom, Lest thou perish!” “And what is that in thy right hand, O Moses?” He said, “It is My rod: on it I lean; with it I beat down fodder For my flocks; and In it I find Have Other uses.” (God) said, “Throw it, O Moses!" He threw it, and behold it was a snake Active in motion. (God) said "Seize it And fear not: We shall return it at once To its former condition… Now draw thy hand Close to thy side: It shall come forth white (And shining), without harm (or stain),- As a another Sign,- In order that we may show thee (Two) of our Greater Signs. Go thou to Pharaoh For he has indeed Transgressed all bounds.” [S. 20:9-24
Behold! Moses said to his family “I perceive A fire; **soon will I bring you From there some information, Or I will Bring you A burning brand to light our fuel That ye may Warm yourselves.” But when he came To the (Fire), a voice Was heard: "Blessed are those In the Fire and those around: And Glory to God, The Lord of the Worlds. "O Moses! Verily I am God, the Exalted In Might, the wise!.. “Now do throw thy rod!” But when he saw it Moving (of its own accord) As if it had been a snake, He turned back in Retreat, And retraced not his steps: “O Moses!” (it was said), “Fear not: truly, in My presence, Those called as apostles Have no fear,- But if Any have done wrong And have thereafter substituted Good to take the place of the evil, Truly, I am Oft-Forgiving, Most Merciful. "Now put thy hand into Thy bosom, and it will Come forth white without stain (Or harm): (These are) among The nine Signs (thou wilt take) To Pharaoh and his people: For they are A people Rebellious in transgression.” But when Our Signs came To them, that should opened their eyes, they said: “This is Sorcery manifest!” And they rejected those Signs In iniquity and arrogance, Though their Souls were convinced Thereof: so see what was The end of those Who acted corruptly. [S. 27:7-14]
Now when Moses had fulfilled The term, and was traveling With his family, he perceived A fire in the direction of Mount Tur. He said To his family: “Tarry ye; I perceive a fire; I hope To bring you from there Some information, or a burning Firebrand that ye may warm yourselves.” But when he came To the (Fire), a voice was heard from the right back Of the valley, from a tree In hallowed ground: “O Moses! Verily I am God, the Lord of the Worlds … Now do thou throw thy rod! But when he saw it Moving (of its own accord) As if it had been a snake, He turned back in retreat and retraced not his steps: “O Moses!” (It was said), "Draw near, and fear not; For thou art of those Who are secure. "Move thy hand into thy bosom, and it will Come forth to thy side (To guard) against fear. Those are the two credentials From thy Lord to Pharaoh And his Chiefs: for truly They are a people Rebellious and wicked.” [S. 28:29-33]
check as well 20:38-40, 28:7,11-13
or
They said: “O Moses! Whether wilt thou That thou throw (first) Or that we be the first to throw?” He said, "Nay, throw ye First!"…20:65-73
then we read:
Moses said to them, “Throw ye- which ye are about to throw!” …26:41
these are a sample.