صحيح البخاري Sahih Bukhari كتاب الأذان The Book of Adhan
بَابُ بَيْنَ كُلِّ أَذَانَيْنِ صَلاَةٌ لِمَنْ شَاءَ:

(16) Chapter. Between every two calls (Adhan and Iqama) there is a Salat (prayer) (that is optional), for the one who wants to offer it.

1 hadith
Hadith 627
حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يَزِيدَ ، قَالَ : حَدَّثَنَا كَهْمَسُ بْنُ الْحَسَنِ ، عَنْ عَبْدِ اللَّهِ بْنِ بُرَيْدَةَ ، عَنْ عَبْدِ اللَّهِ بْنِ مُغَفَّل ، قَالَ : قَالَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ : " بَيْنَ كُلِّ أَذَانَيْنِ صَلَاةٌ ، بَيْنَ كُلِّ أَذَانَيْنِ صَلَاةٌ ، ثُمَّ قَالَ فِي الثَّالِثَةِ 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).
Hadith Reference Sahih Bukhari / The Book of Adhan / Hadith: 627
Hadith Grading محدثین: أحاديث صحيح البخاريّ كلّها صحيحة