Sunan an-Nasa'i, Volume 2, Book 20, Hadith 1768 (DarusSalam) ⓘ
It was narrated from Ibn 'Umar that Hafsah said: "The Messenger of Allah used to pray two brief rak'ahs between the call (the Adhan) and the prayer."
أَخْبَرَنَا إِسْحَاقُ بْنُ مَنْصُورٍ، قَالَ أَنْبَأَنَا يَحْيَى، قَالَ حَدَّثَنَا الأَوْزَاعِيُّ، قَالَ حَدَّثَنِي يَحْيَى، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، عَنْ حَفْصَةَ، قَالَتْ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يَرْكَعُ بَيْنَ النِّدَاءِ وَالصَّلاَةِ رَكْعَتَيْنِ خَفِيفَتَيْنِ .
also referenced under: Hadith 1767 (Reference) & Book 20, Hadith 170 (In-Book)