Allah's statement,

﴿مَثْنَى وَثُلَـثَ وَرُبَاعَ﴾

(two or three, or four), means, marry as many women as you like, other than the orphan girls, two, three or four. We should mention that Allah's statement in another Ayah,

﴿جَاعِلِ الْمَلَـئِكَةِ رُسُلاً أُوْلِى أَجْنِحَةٍ مَّثْنَى وَثُلَـثَ وَرُبَـعَ﴾

(Who made the angels messengers with wings, - two or three or four) ﴿35:1﴾, does not mean that other angels do not have more than four wings, as there are proofs that some angels do have more wings. Yet, men are prohibited from marrying more than four wives, as the Ayah decrees, since the Ayah specifies what men are allowed of wives, as Ibn `Abbas and the majority of scholars stated. If it were allowed for them to have more than four wives, the Ayah would have mentioned it.

Imam Ahmad recorded that Salim said that his father said that Ghilan bin Salamah Ath-Thaqafi had ten wives when he became Muslim, and the Prophet said to him, "Choose any four of them (and divorce the rest).'' During the reign of `Umar, Ghilan divorced his remaining wives and divided his money between his children. When `Umar heard news of this, he said to Ghilan, "I think that the devil has conveyed to your heart the news of your imminent death, from what the devil hears during his eavesdropping. It may as well be that you will not remain alive but for a little longer. By Allah! You will take back your wives and your money, or I will take possession of this all and will order that your grave be stoned as is the case with the grave of Abu Righal (from Thamud, who was saved from their fate because he was in the Sacred Area. But, when he left it, he was tormented like they were).'' Ash-Shafi`i, At-Tirmidhi, Ibn Majah, Ad-Daraqutni and Al-Bayhaqi collected this Hadith up to the Prophet's statement, "Choose any four of them.'' Only Ahmad collected the full version of this Hadith.

Therefore, had it been allowed for men to marry more than four women at the same time, the Prophet would have allowed Ghilan to keep more than four of his wives since they all embraced Islam with him. When the Prophet commanded him to keep just four of them and divorce the rest, this indicated that men are not allowed to keep more than four wives at a time under any circumstances. If this is the case concerning those who already had more than four wives upon embracing Islam, then this ruling applies even more so to marrying more than four.