Al-Aḥzāb: 52
{لا يحل لك}
It is read in the masculine form (lā yaḥillu), because the feminine plural is not a "true" feminine (ghayr ḥaqīqī). If the masculine is permissible without separation in the words of the Almighty, "And women said" (wa-qāla niswatan - Yusuf: 30), then it is even more permissible when there is separation.
{من بعد}
Meaning: after the nine. For nine was the quota (niṣāb) of the Messenger of Allah (ﷺ) regarding wives, just as four is the quota for his nation. Thus, it is not lawful for him to exceed this quota.
{ولا أن تبدل بهن}
Meaning: nor to exchange these nine for other wives, whether replacing all of them or some of them. He intended for the nine to remain with him as an honor and a reward for what they chose and were content with. Thus, the Prophet (ﷺ) was restricted to them. These are the nine he left behind upon his death: ‘Ā’ishah bint Abī Bakr, Ḥafṣah bint ‘Umar, Umm Ḥabībah bint Abī Sufyān, Sawdah bint Zam‘ah, Umm Salamah bint Abī Umayyah, Ṣafiyyah bint Ḥuyayy al-Khaybariyyah, Maymūnah bint al-Ḥārith al-Hilāliyyah, Zaynab bint Jaḥsh al-Asadiyyah, and Juwayriyyah bint al-Ḥārith al-Muṣṭaliqiyyah (may Allah be pleased with them).
The "min" in {من أزواج} is for the emphasis of negation, and its benefit is the inclusion of the entire genus of wives under the prohibition. It is also said: it means women are not lawful for you after the women whose lawfulness was explicitly stated for you from the four categories (Bedouin women, foreign women, People of the Book, or slave-girls via marriage).
Regarding the prohibition of "exchange" (tabaddul): it refers to the practice of the Pre-Islamic era (Jāhiliyyah), where a man would say to another, "Exchange your wife with me, and I will exchange my wife with you," and each would relinquish his wife to the other.
It is narrated that ‘Uyaynah ibn Ḥiṣn entered upon the Prophet (ﷺ) while ‘Ā’ishah was with him, without asking permission. The Messenger of Allah (ﷺ) said, "O ‘Uyaynah, where is the request for permission?" He replied, "O Messenger of Allah, I have never asked permission of any man since I reached maturity." Then he said, "Who is this beautiful woman beside you?" The Prophet (ﷺ) replied, "This is ‘Ā’ishah, Mother of the Believers." ‘Uyaynah said, "Shall I not exchange her for a more beautiful woman?" The Prophet (ﷺ) said, "Allah has forbidden that." When he left, ‘Ā’ishah (ra) asked, "Who is this, O Messenger of Allah?" He replied, "A foolish man who is obeyed; yet, despite what you see, he is the leader of his people."
Regarding ‘Ā’ishah (ra): "The Messenger of Allah (ﷺ) did not die until women were made lawful for him," meaning the verse was abrogated. If it was abrogated, it was either by the Sunnah or by the words of the Almighty: {We have made lawful to you your wives} (Al-Aḥzāb: 50), as the order of revelation does not follow the order of the Muṣḥaf.
{ولو أعجبك}
This is in the state of a circumstantial qualifier (ḥāl) from the subject, which is the pronoun in {tabaddal}, not from the object {min azwāj}, because the latter is too indefinite. Its estimation is: "even if your admiration for them were assumed." It is said: it refers to Asmā’ bint ‘Umays al-Khath‘amiyyah, the wife of Ja‘far ibn Abī Ṭālib, and the meaning is that she was among those whose beauty he admired. He excepted slave-girls from what was forbidden to him.
{رقيبا}
Meaning: a guardian, an observer. This is a warning against overstepping His limits and crossing from the lawful into the forbidden.