In the name of Allah, the Beneficent, the Merciful.
[24.1] (This is) a chapter which We have revealed and made obligatory and in which We have revealed clear communications that you may be mindful.
[24.2] (As for) the fornicatress and the fornicator, flog each of them, (giving) a hundred stripes, and let not pity for them detain you in the matter of obedience to Allah, if you believe in Allah and the last day, and let a party of believers witness their chastisement.
[24.3] The fornicator shall not marry any but a fornicatress or idolatress, and (as for) the fornicatress, none shall marry her but a fornicator or an idolater; and it is forbidden to the believers.
[24.4] And those who accuse free women then do not bring four witnesses, flog them, (giving) eighty stripes, and do not admit any evidence from them ever; and these it is that are the transgressors,
“Narrated Ibn ‘Abbas
‘Umar said, “I am afraid that after a long time has passed, people may say, “We do not find the Verses of the Rajam (stoning to death) in the Holy Book,” and consequently they may go astray by leaving an obligation that Allah has revealed. Lo! I confirm that the penalty of Rajam be inflicted on him who commits illegal sexual intercourse, if he is already married and the crime is proved by witnesses or pregnancy or confession.” Sufyan added, “I have memorized this narration in this way.” ‘Umar added, “Surely Allah’s Apostle carried out the penalty of Rajam, and so did we after him.”
If the Quran contains the eternal words of Allah then these words must represent the eternal will of Allah. If Allah is immutable, which would be necessary if he is God, he does not change his mind about whether a moral human action is right or wrong and the just penalty to accord with it. This would also be an injustice to those who were punished unequally for the same offense would it not? His wisdom would also be questionable if this were the case.
Once Allah has sent the angel to recite he has no way of turning back by giving another recitation as the Quran would contain contradictory rulings on the same offense. So we see here that Mohammed is greater than Allah because he never needed to change anything he had done. He always got it right first time.
A curiosity here is that accusing a woman of sexual infidelity is only twenty lashes less worth of punishment than actually committing the act of fornication itself. Also the requirement for four witnesses who also had to be in the immediate presence as eye witnesses of all the details. This shows a strong emphasis in Islam on covering things up, if the perpetrators are Muslims, so that the Ummah does not come in to disrepute and by implication, Islam itself. This is more important than actually punishing the act itself. This is one reason why a lot of pressure is put on non-Muslims to settle out of court if they have a justifiable grievance against a Muslim.