Hadith: When the Iqāmah (second call ) for prayer is pronounced, no prayer is to be offered but the obligatory one

عَنْ أَبِي هُرَيْرَةَ رَضِيَ اللهُ عَنْهُ عَنِ النَّبِيِّ صلَّى اللَّهُ عليْه وسلَّمَ، قَالَ:
«إِذَا أُقِيمَتِ الصَّلَاةُ فَلَا صَلَاةَ إلَّا المَكْتُوبَةُ».
[صحيح] - [رواه مسلم] - [صحيح مسلم: 710]

Abu Hurayrah (may Allah be pleased with him) reported that the Prophet (ﷺ) said:
"When the Iqāmah (second call ) for prayer is pronounced, no prayer is to be offered but the obligatory one."
[Authentic hadith] - [Narrated by Muslim] - [Sahih Muslim - 710]

Explanation

The Prophet (ﷺ) prohibited anyone who is in the mosque from beginning a voluntary prayer after the Iqāmah has been pronounced for the obligatory prayer.

Benefits from the Hadith

1. The prohibition of performing a voluntary prayer when the Iqāmah for the obligatory prayer has been pronounced and one is in the mosque.
2. The prohibition of commencing a voluntary prayer after the Iqāmah for prayer has been pronounced, whether it is a regular Sunnah prayer such as those of Fajr and Zhuhr or any other voluntary prayer.
3. If the (congregational) prayer is called to begin while a person is performing a voluntary prayer, and there remains less than one Rak‘ah to complete, he should finish it quickly. Otherwise, he should end it in order to attain the virtue of the opening Takbīr (with the congregation).