This hadith has been narrated by the same chain of transmitters and in the hadith narrated by Usama the words are:" When it was dawn
Hadis 1683 — Sahih Muslim 6:113
وَحَدَّثَنَاهُ مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنَا ابْنُ أَبِي عَدِيٍّ، عَنْ هِشَامٍ، عَنْ يَحْيَى، عَنْ أَبِي سَلَمَةَ، عَنْ عَائِشَةَ، أَنَّ نَبِيَّ اللَّهِ صلى الله عليه وسلم كَانَ يُصَلِّي رَكْعَتَيْنِ بَيْنَ النِّدَاءِ وَالإِقَامَةِ مِنْ صَلاَةِ الصُّبْحِ .
A'isha reported that the Messenger of Allah (ﷺ) used to observe two (supererogatory) rak'ahs in between the call to prayer and the Iqama of the dawn prayer
A'isha reported that the Messenger of Allah (ﷺ) observed two rak'ahs of the dawn prayer and he shortened them (to the extent) that I (out of surprise) said:Did he recite in them Surah Fatiha (only)?
A'isha reported:When it was dawn, the Messenger of Allah (ﷺ) observed two rak'ahs, and I would say: Does he recite only the opening chapter of the Qur'an in it?
Hadis 1686 — Sahih Muslim 6:116
وَحَدَّثَنِي زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا يَحْيَى بْنُ سَعِيدٍ، عَنِ ابْنِ جُرَيْجٍ، قَالَ حَدَّثَنِي عَطَاءٌ، عَنْ عُبَيْدِ بْنِ عُمَيْرٍ، عَنْ عَائِشَةَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم لَمْ يَكُنْ عَلَى شَىْءٍ مِنَ النَّوَافِلِ أَشَدَّ مُعَاهَدَةً مِنْهُ عَلَى رَكْعَتَيْنِ قَبْلَ الصُّبْحِ .
A'isha reported that the Apostle (ﷺ) was not so much particular about observing supererogatory rak'ahs as in case of the two rak'ahs of the dawn prayer
A'isha reported:I have never seen the Messenger of Allah (ﷺ) hastening as much in observing supererogatory as two rak'ahs before the (Fard) of the dawn prayer