[Machine] The mu'adhin used to pray two light optional units of prayer after the Fajr prayer, just like the Prophet ﷺ .
كَانَ الْمُؤَذِّنُ إِذَا سَكَتَ مِنْ صَلَاةِ الصُّبْحِصَلَّى رَكْعَتَيْنِ خَفِيفَتَيْنِ تَعْنِي النَّبِيَّ ﷺ
The Prophet ﷺ used to offer two light rakʿat between the Adhan and the Iqama of the Fajr prayer.
عَنْ عَائِشَةَ كَانَ النَّبِيُّ ﷺ يُصَلِّي رَكْعَتَيْنِ خَفِيفَتَيْنِ بَيْنَ النِّدَاءِ وَالإِقَامَةِ مِنْ صَلاَةِ الصُّبْحِ
Ibn 'Umar reported that Hafsa, the Mother of the Believers, informed him that when the Mu'adhdhin became silent after calling (people) to the dawn prayer, the Messenger of Allah ﷺ commenced the dawn (prayer) when it dawned by observing two short rak'ahs before the commencement of the (Fard) prayer.
أَنَّ رَسُولَ اللَّهِ ﷺ كَانَ إِذَا سَكَتَ الْمُؤَذِّنُ مِنَ الأَذَانِ لِصَلاَةِ الصُّبْحِ وَبَدَا الصُّبْحُ رَكَعَ رَكْعَتَيْنِ خَفِيفَتَيْنِ قَبْلَ أَنْ تُقَامَ الصَّلاَةُ
Told him that when the Muaddhin fell silent, Messenger of Allah ﷺ would pray two brief rak'ahs.
أَنَّ رَسُولَ اللَّهِ ﷺ كَانَ إِذَا سَكَتَ الْمُؤَذِّنُ صَلَّى رَكْعَتَيْنِ خَفِيفَتَيْنِ
that when the Muaddhin fell silent following the call to Subh prayer and dawn had broken, he would pray two brief rak'ahs before getting up to pray.
أَنَّ رَسُولَ اللَّهِ ﷺ كَانَ إِذَا سَكَتَ الْمُؤَذِّنُ مِنَ الأَذَانِ لِصَلاَةِ الصُّبْحِ وَبَدَا الصُّبْحُ صَلَّى رَكْعَتَيْنِ خَفِيفَتَيْنِ قَبْلَ أَنْ تُقَامَ الصَّلاَةُ
that when the Muaddhin fell silent following the call to Subh prayer and dawn had broken, he would pray two brief rak'ahs before getting up to pray. (Using translation from Nasāʾī 1773)
عَنْ حَفْصَةَ زَوْجِ النَّبِيِّ ﷺ قَالَتْ كَانَ رَسُولُ اللَّهِ ﷺ «إِذَا سَكَتَ الْمُؤَذِّنُ مِنْ أَذَانِ الصُّبْحِ وَبَدَا الصُّبْحُ صَلَّى رَكْعَتَيْنِ خَفِيفَتَيْنِ قَبْلَ أَنْ تُقَامَ الصَّلَاةُ»
Ibn 'Umar reported that Hafsa, the Mother of the Believers, informed him that when the Mu'adhdhin became silent after calling (people) to the dawn prayer, the Messenger of Allah ﷺ commenced the dawn (prayer) when it dawned by observing two short rak'ahs before the commencement of the (Fard) prayer. (Using translation from Muslim 723a)
أَنَّ النَّبِيَّ ﷺ كَانَ «إِذَا سَكَتَ الْمُؤَذِّنُ مِنَ الْأَذَانِ لِصَلَاةِ الصُّبْحِ وَبَعْدَ الصُّبْحِ صَلَّى رَكْعَتَيْنِ خَفِيفَتَيْنِ قَبْلَ أَنْ تُقَامَ الصَّلَاةُ»