Sunan an-Nasa'i, Hadith 1768 ⓘ
It was narrated from Abu Salamah and Nafi', from Ibn Umar, from Hafsah that: The Prophet used to pray two brief rak'ahs between the call (The adhan) and the Iqamah, the two rak'ahs of Fajr.
أَخْبَرَنَا هِشَامُ بْنُ عَمَّارٍ، قَالَ حَدَّثَنَا يَحْيَى، - يَعْنِي ابْنَ حَمْزَةَ - قَالَ حَدَّثَنَا الأَوْزَاعِيُّ، عَنْ يَحْيَى، عَنْ أَبِي سَلَمَةَ، قَالَ هُوَ وَنَافِعٌ عَنِ ابْنِ عُمَرَ، عَنْ حَفْصَةَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم كَانَ يُصَلِّي بَيْنَ النِّدَاءِ وَالإِقَامَةِ رَكْعَتَيْنِ خَفِيفَتَيْنِ رَكْعَتَىِ الْفَجْرِ .
also referenced under: Book 20, Hadith 171 (In-Book) & Volume 2, Book 20, Hadith 1769 (DarusSalam)