مَا كَانَ مُحَمَّدٌ أَبَا أَحَدٍ مِنْ رِجَالِكُمْ وَلَكِنْ رَسُولَ اللَّهِ وَخَاتَمَ النَّبِيِّينَ وَكَانَ اللَّهُ بِكُلِّ شَيْءٍ عَلِيمًا ﴿۴۰﴾ يَا أَيُّهَا الَّذِينَ آمَنُوا اذْكُرُوا اللَّهَ ذِكْرًا كَثِيرًا ﴿۴۱﴾

﴾40﴿ Maa kaana Muhammmadun abaaa ahadim mir rijaalikum wa laakir Rasoolal laahi wa Khaataman Nabiyyeen; wa kaanal laahu bikulli shai'in 'Aleema
﴾41﴿ Yaaa aiyuhal lazeena aamanuz kurul laaha zikran kaseera

﴾40﴿ Muhammad, peace and blessings be upon him, is not the father of any of your men, but he is the Messenger of Allah, the Exalted, and the Seal of all the Prophets. And Allah, the Exalted, is All-Knowing over all things
﴾41﴿ O believers, remember Allah, the Exalted, with much remembrance

[40] This is an address to the believers, providing responses to the objections people raised regarding the Prophet’s (May Allah bless him and give him peace) marriage to Zaynab (may Allah be pleased with her):
1. First objection: The Prophet married the wife of his adopted son? The answer is: "Mā kāna Muḥammadun abā aḥadin min rijālikum" — Muhammad is not the father of any of your men.
Meaning, none of the Prophet’s male children reached manhood, as all his sons died in childhood.
Although he had four daughters who reached adulthood and married, the phrase "rijālikum" (your men) implies that none of you can be his true sons — thus, this negates both actual and adopted (metaphorical) sons.
2. Second objection: Even if she wasn’t his real son’s wife, why was there a need to marry Zaynab? People would still mock him. The answer: "Wa lākin Rasūl Allāh" — But he is the Messenger of Allah.
Meaning, this issue involved refuting a false custom of shirk, so it was essential to convey it — and as a prophet, it was his duty to deliver the message, regardless of people’s criticism.
3. Third objection: Why did he have to be the one to convey this? Couldn’t another prophet come after him to deliver it? The answer: "Wa khātam al-nabiyyīn" — He is the Seal of the Prophets.
There is no prophet to come after him, so he had to fulfill this task himself.
4. Fourth objection: How can we be sure that no prophet will come after him? The answer: "Wa kāna Allāhu bi-kulli shay’in ‘alīmā" — And Allah is All-Knowing of everything.
Meaning, Allah has the knowledge, and it is He who has declared the finality of prophethood — so there is no room for doubt.
Note: From the content and flow of the verse, it is clearly understood that the meaning of "Khātam al-Nabiyyīn" is that this Prophet is the last — no prophet will come after him.
This is also affirmed in a sound hadith: "Wa anā khātam al-nabiyyīn, lā nabiyya ba‘dī" (Abū Dāwūd) — “I am the Seal of the Prophets; there is no prophet after me.”
And in another authentic hadith: "Wa anā al-‘āqib, wa al-‘āqib alladhī laysa ba‘dahu nabiyyun" — “I am the Last, and the Last is the one after whom there is no prophet.”
In addition, there are many more ahādīth on this subject.
Thus, it becomes clear that the meaning of Khātam al-Nabiyyīn is "the final one", and this is how it has been defined in Lisān al-‘Arab (a classical Arabic dictionary): "Khātam al-nabiyyīn: ākhiruhum" — “The Seal of the Prophets: the last of them.”
So this verse is a definitive, clear proof that our Prophet (May Allah bless him and give him peace) is the final Prophet, and no new prophet can be created after him.
To deny this is to deny a definitive, unequivocal text, and that is clear disbelief (kufr).
As for the descent of ‘Īsā (peace be upon him) from the heavens, there are mutawātir (mass-transmitted) ahādīth affirming it.
However, his return does not affect the finality of prophethood, because he is a previous prophet, and when he returns, no new revelation will come to him.
Instead, he will judge according to the Sharī‘ah of our Prophet (May Allah bless him and give him peace).
[41,42] From this verse until the end of the surah is the fourth section.
Within it, there are five addresses to the Prophet (May Allah bless him and give him peace) — in verses 45, 48, 50, 52, and 59,
and seven addresses to the believers — in verses 41, 42, 49, 53, 56, 69, and 70.
There are also eight verses of warning (takhwīf) — in verses 57, 58, 64, 65, 66, 68, 72,
and one rebuke to the hypocrites for asking unnecessary questions — in verse 63.
In verses 41 and 42, there is an address to the believers with two commands:
1. To make abundant remembrance (dhikr) of Allah,
2. And to glorify Him constantly.
Connection to the previous verse: After refuting the doubts and objections people raised about the Prophet (May Allah bless him and give him peace), this verse now presents dhikr (remembrance) as the cure for doubts and misconceptions.
"Dhikran" — this word is general and includes all types of worship: physical (badaniyyah), financial (māliyah), internal (qalbiyyah), and verbal (lisāniyyah).
"Kathīran" — refers to those who perform dhikr in abundance, with sincerity of heart and adherence to the Sunnah.
"Bukratan wa aṣīlā" — these two times (morning and evening) have great virtue, which is why they are mentioned specifically. However, other times are also included, or it may mean the entire day and night.
"Tasbīḥ" — means saying “Subḥānallāh” with the tongue, along with firm belief in the heart. It also includes performing prayer (ṣalāh) as a form of glorification.