“When the prayer is called for, there is no prayer except the prescribed one.”

Narrated by Muslim (no. 710), from the ḥadīth of Abū Hurayrah (may Allah be pleased with him).

Brief Explanation of the Hadith

This ḥadīth establishes a great principle in the Sharīʿah: the obligatory prayer takes precedence over the voluntary prayer. Thus, once the prayer has been established, it is not permissible for a Muslim to begin any voluntary prayer—neither the greeting of the mosque nor the regular Sunnah prayers, even the Sunnah of Fajr. Rather, the duty is to proceed directly to the obligatory prayer alone and not to busy oneself with anything else, in accordance with the apparent meaning of the ḥadīth.
As for the one who has already begun a voluntary prayer and then the iqāmah is called, he should cut it off if he is still at the beginning, and complete it briefly if he is at the end. Some scholars have restricted this by saying: if he has already completed a rakʿah of the voluntary prayer, then he may finish it and then join the imām—citing as evidence the ḥadīth: “Whoever catches a rakʿah of the prayer has caught the prayer.” The negation in the ḥadīth is therefore intended as a prohibition.
And the scholars have carried this ḥadīth upon two possible meanings:
• Negation of validity: that the voluntary prayer itself is not valid once the iqāmah has been called.
• Negation of completeness: meaning it is valid in principle, but deficient in reward—and this is the view held by the majority.
The wisdom in this Prophetic guidance is apparent in several matters:
• Observing the obligatory prayer from its beginning with the Imām.
• Catching the Takbīrat al-Ihrām, which is among the greatest of virtues.
• Ensuring the unity of the rows and the congregation, and avoiding anything that might cause dispute or objection to the Imāms.
Thus, the ḥadīth as a whole trains the Muslim to prioritize the most important over what is less important, to give due care to the obligatory acts before the supererogatory ones, and to magnify the status of the congregational prayer and its great rank.
And the apparent meaning of the ḥadīth is that it is not permissible to begin a voluntary prayer after the iqāmah has been called, whether in one’s house or elsewhere. Rather, if he wishes, he may make it up after the obligatory prayer.