Muwatta Malik, Book 7, Hadith 29 (USC-MSA) ⓘ

Yahya related to me from Malik from Nafi from Abdullah ibn Umar that Hafsa, the wife of the Prophet, may Allah bless him and grant him peace, told him that the Messenger of Allah, may Allah bless him and grant him peace, used to pray two quick rakas when the muadhdhin had finished the adhan for the subh prayer, before the iqama was said for the prayer.

حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ حَفْصَةَ، زَوْجَ النَّبِيِّ صلى الله عليه وسلم أَخْبَرَتْهُ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ إِذَا سَكَتَ الْمُؤَذِّنُ عَنِ الأَذَانِ لِصَلاَةِ الصُّبْحِ صَلَّى رَكْعَتَيْنِ خَفِيفَتَيْنِ قَبْلَ أَنْ تُقَامَ الصَّلاَةُ ‏.‏