Sunan Ibn Majah, Volume 2, Book 5, Hadith 1162 (DarusSalam) ⓘ
It was narrated that ‘Abdullah bin Mughaffal said: “The Prophet of Allah said: ‘Between every two Adhans there is a prayer.’ He said it three times, and on the third time he said, ‘For those who wish.’”*
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا أَبُو أُسَامَةَ، وَوَكِيعٌ، عَنْ كَهْمَسٍ، حَدَّثَنَا عَبْدُ اللَّهِ بْنُ بُرَيْدَةَ، عَنْ عَبْدِ اللَّهِ بْنِ مُغَفَّلٍ، قَالَ قَالَ نَبِيُّ اللَّهِ ـ صلى الله عليه وسلم ـ " بَيْنَ كُلِّ أَذَانَيْنِ صَلاَةٌ " . قَالَهَا ثَلاَثًا قَالَ فِي الثَّالِثَةِ " لِمَنْ شَاءَ " .
also referenced under: Hadith 1162 (Reference) & Book 5, Hadith 1217 (In-Book)