Sahih al-Bukhari 612
In-book no 612حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يَزِيدَ، قَالَ حَدَّثَنَا كَهْمَسُ بْنُ الْحَسَنِ، عَنْ عَبْدِ اللَّهِ بْنِ بُرَيْدَةَ، عَنْ عَبْدِ اللَّهِ بْنِ مُغَفَّلٍ، قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم " بَيْنَ كُلِّ أَذَانَيْنِ صَلاَةٌ بَيْنَ كُلِّ أَذَانَيْنِ صَلاَةٌ ـ ثُمَّ قَالَ فِي الثَّالِثَةِ ـ لِمَنْ شَاءَ ".
Narrated `Abdullah bin Mughaffal: The prophet said, "There is a prayer between the two Adhans (Adhan and Iqama), there is a prayer between the two Adhans." And then while saying it the third time he added, "For the one who wants to (pray).