The Quran Verse (The Rule for Muslims)
Surah 4:3:
And if you fear that you will not deal justly with the orphan girls, then marry those that please you of women, two or three or four. But if you fear that you will not be just, then one or those your right hand possesses. That is more suitable that you may not incline.
The Relevant Source Text (The Contradictory Exception)
Surah 33:50:
O Prophet, indeed We have made lawful to you your wives to whom you have given their due compensation... and any believing woman if she gives herself to the Prophet if the Prophet wishes to marry her, only for you, excluding the believers. We certainly know what We have made obligatory upon them concerning their wives...
Surah 4 establishes a strict, supposedly divine moral limit on polygamy (maximum of four wives).
However, later in the Quran, God "reveals" a highly convenient exception that applies only to Muhammad, allowing him unlimited wives and the ability to marry women without paying a dowry. To the critical scholar, this is not the behavior of an eternal, unchanging deity, but the mark of a human author altering the "divine" law to accommodate his own personal and sexual desires.
Aisha, Muhammad's child bride, even noted this convenience in a famous Hadith (Bukhari 4788), saying, "I feel that your Lord hastens in fulfilling your wishes and desires."