بِسْمِ ٱللَّهِ ٱلرَّحْمَٰنِ ٱلرَّحِيمِ
In the name of Allah, the All-Beneficent, the All-Merciful
إِذَا جَاءَ نَصْرُ اللَّهِ وَالْفَتْحُ
When Allah’s help comes with victory,
وَرَأَيْتَ النَّاسَ يَدْخُلُونَ فِي دِينِ اللَّهِ أَفْوَاجًا
and you see the people entering Allah’s religion in throngs,
English translation: Ali Quli Qarai
These two āyāt are a dated, conditional announcement: a when-clause whose answer is held back to āyah 3. Every present source reads the opening as a glad tiding of a victory not yet realized. Al-Ṭūsī (al-Tibyān) calls it plainly "a promise from Allah to His Prophet of help through victory before the matter came to pass," and — citing al-Ḥasan and Mujāhid — identifies the promised event as the conquest of Mecca and God's help against the disbelievers of Quraysh. Al-Ṭabarsī (Majmaʿ al-Bayān) agrees almost verbatim: naṣr is help "against those who showed you enmity, namely Quraysh," and fatḥ is "the conquest of Mecca," a bishāra given "before the matter came to pass."
Why "the conquest of Mecca" specifically? Al-Ṭabāṭabāʾī (al-Mīzān) supplies the reasoning the others leave implicit. The future-pointing idhā requires an as-yet-unfulfilled event; it cannot mean victory in the generic sense (his battles, the faith of the Anṣār or of Yemen), because that would not fit the next clause, "you see the people entering... in throngs"; nor can it be al-Ḥudaybiyya — itself named a "clear victory" in 48:1 — because āyah 2 does not apply to it. The "clearest" referent is the conquest of Mecca, "the mother of his conquests... by which the edifice of polytheism was demolished in the Arabian Peninsula." On this basis al-Mīzān dates the surah as Medinan, after al-Ḥudaybiyya and before the conquest, linking it to the promise of "a mighty help" in 48:1–3. The Enlightening Commentary concurs that the intended victory is "undoubtedly the conquest of Mecca," the bloodless triumph after which whole Arabian tribes gave allegiance — and adds the historical note that the pagans took the fall of the protected Sanctuary (which God had shielded even from the People of the Elephant) as a sign of the Prophet's legitimacy.
"Entering Allah's religion in throngs." Ṭabarsī and Ṭūsī give the same lexical analysis: a fawj is "a group out of groups," so people came "group after group, by whole tribes," where before they had entered "one by one or two by two." Al-Mīzān grounds this in al-Rāghib's definition — fawj = "the passing, hastening group" — and fixes "Allah's religion" as Islam (3:19, "the religion with Allah is Islam"). Both classical masters note a secondary sense of dīn as "obedience" (its root being "requital"), citing 12:76.
The distinctively Imāmī voices. Tafsīr al-Qummī anchors the revelation not at Mecca but at Minā during the Farewell Pilgrimage, making the surah the trigger for the Prophet's announcement "My own death has been announced to me," followed at the Mosque of al-Khayf by the Ḥadīth al-Thaqalayn — "I am leaving among you two weighty things... the Book of Allah and my progeny." This timing openly conflicts with al-Mīzān's before-the-conquest dating; both are preserved here without harmonizing them. Al-Baḥrānī (al-Burhān) adds a narration (al-Ṭūsī's and al-Mufīd's Amālī) in which the Prophet, on this verse, charges ʿAlī with jihād against the people of fitna after him — a sectarian, polemical report whose chain is unvetted and which is recorded as transmitted, not endorsed (flagged for review). The throughline across all sources: the help is God's, the goal is people's guidance, and the victory's true measure is not power but the worship to which āyah 3 will summon the Prophet.