Sahih al-Bukhari 637
Sahih al-Bukhari · Book 10: Call to Prayers (Adhaan) · When should the people get up for the Salat (prayer) if they see the Imam (the person leading Salat) during the Iqama?
Narrated `Abdullah bin Abi Qatada:
حَدَّثَنَا مُسْلِمُ بْنُ إِبْرَاهِيمَ ، قَالَ حَدَّثَنَا هِشَامٌ ، قَالَ كَتَبَ إِلَىَّ يَحْيَى عَنْ عَبْدِ اللَّهِ بْنِ أَبِي قَتَادَةَ ، عَنْ أَبِيهِ ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِذَا أُقِيمَتِ الصَّلاَةُ فَلاَ تَقُومُوا حَتَّى تَرَوْنِي " .
My father said. "Allah's Messenger (ﷺ) said, 'If the Iqama is pronounced then do not stand for the prayer till you see me (in front of you).' "