Translated by Zameelur Rahman
Al-Shafi‘i said: “Allah (Glorified is He) singled out the Messenger of Allah by obligating on him things which He alleviated from other than him, in order to increase his (Allah bless him and grant him peace) sanctity, and He permitted for him things which He made unlawful for other than him, in order to increase his honour and his exaltation.”
From this category is [the permission of] having more than four [wives]. This was permitted [for him] so that he ascends in the hearts of the Arabs in esteem and glory, because they would boast over sexual prowess. Furthermore, in terms of perfect power and moderate constitution, he was at the level of perfection attested to by the reports, and whoever was such, the precursors to this door [of perfection] would be dominant over him.
Furthermore, those besides him were forbidden from more than four [wives] for fear of injustice, as alluded to in the verse: “But, if you fear that you will not maintain equity, then [marry only] one.” (4:3) And this reason is inapplicable with respect to him (Allah bless him and grant him peace).
That this is the reason for forbidding those besides him is proven by [the fact] that Allah (Glorified is He) permitted for them whatever [quantity] of slave women they have [financial] ability over, as in His (Exalted is He) statement: “Or what your right hands possess” (4:3), because slave women did not have rights over sexual intercourse such that injustice would be feared therein.
Furthermore, it is not permissible for him [i.e. the Prophet (peace be upon him)] to seek pleasure in what is not permissible for him, nor to seek what is in the hands of men, and the condition at that time was not accommodating for the acquisition of [many] slave women. Hence, free women were made available to him. And Allah chose for him the best of the two kinds [i.e. free women over slave women]. This is why some of the Salaf said: “Free [non-Muslim] covenanted women were not permissible for him to marry, as opposed to other than him from his ummah.” Others said: “So that a disbeliever would not become a mother of the believers.”
This is in Sharh al-Ubbi.
The weak slave (Allah pardon him) says:
The teacher of our teachers, Hakim al-Ummah al-Thanawi (may Allah sanctify his secret), mentioned another wisdom behind the abundance of his (Allah bless him and grant him peace) wives, which is that:
He (upon him blessing and peace) was sent to this world to be an excellent example in all things, and so that his ummah imitates him in all walks of life, and in order for this to be possible it is necessary that no part of his personal or his communal life is hidden to his ummah, and that the ummah are privy to the circumstances of his house and his private life by that degree of certainty and that abundance [of reports] by which they know his circumstances outside the house. And indeed these circumstances are not revealed to any besides his (Allah bless him and grant him peace) wives, and this is why the number of his (Allah bless him and grant him peace) wives after Khadijah, the Magnificent, reached ten, because ten is the least number for recurrent transmission (tawatur), and when the number of his wives reached ten, Allah (Exalted is He) forbade him from increasing on this number, as was said in the explanation of His (Exalted is He) saying: “Women are not permitted for you thereafter” (33:52) to the end [of the verse]. Refer to al-Tafsir al-Kabir.
And in this number of wives there are three secrets which Shaykh al-Thanawi (Allah have mercy on him) mentioned:
First, that it is the least of “the plurality of abundance” (jam‘ al-kathrah).
Second, that it is the least number for recurrent transmission (tawatur).
Third, that it agrees with the number of years the Messenger of Allah (Allah bless him and grant him peace) resided in Madinah (i.e. 10).
This is from his treatise Kathrat al-Azwaj li Sahib al-Mi‘raj.
This is supported by the fact that he (Allah bless him and grant him peace) did not spend his youth and his period of manliness but with one widowed woman many years his senior, despite what was presented before him of chaste Arab virgins; and his wives did not increase in number except after he reached fifty three years of age, and all of them were widows, besides ‘A’ishah (Allah be pleased with her). Would one who does not wish but to fulfil his desires and satisfy his lust do this? Never! Then again, never! But his (Allah bless him and grant him peace) objective was only to make the conditions of his house reach the ummah by that abundance [of reports] by which his circumstances outside the house reached [them], and that would not have been possible unless his wives were no fewer than ten. This is why we see that about half of religion did not reach us but through the medium of his (Allah bless him and grant him peace) wives.
(Takmilah Fath al-Mulhim 1:113-4)