Between every two calls, there is a prayer

Sahih Muslim · Book 6 · Hadith 838 a

وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا أَبُو أُسَامَةَ، وَوَكِيعٌ، عَنْ كَهْمَسٍ، قَالَ حَدَّثَنَا عَبْدُ اللَّهِ بْنُ بُرَيْدَةَ، عَنْ عَبْدِ اللَّهِ بْنِ مُغَفَّلٍ الْمُزَنِيِّ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ بَيْنَ كُلِّ أَذَانَيْنِ صَلاَةٌ - قَالَهَا ثَلاَثًا قَالَ فِي الثَّالِثَةِ - لِمَنْ شَاءَ ‏"‏ ‏.‏

Abdullah b. Mughaffal reported Allah's Messenger (ﷺ) u saying: There Is between the two calls (Adhan and Iqama) a prayer. And he mentioned it three times, and at the third time he said: This applies to those who wish to…

Sahih Muslim · Book 6 · Hadith 838 b

وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا عَبْدُ الأَعْلَى، عَنِ الْجُرَيْرِيِّ، عَنْ عَبْدِ اللَّهِ، بْنِ بُرَيْدَةَ عَنْ عَبْدِ اللَّهِ بْنِ مُغَفَّلٍ، عَنِ النَّبِيِّ صلى الله عليه وسلم ‏.‏ مِثْلَهُ إِلاَّ أَنَّهُ قَالَ فِي الرَّابِعَةِ ‏"‏ لِمَنْ شَاءَ ‏"‏ ‏.‏

This hadith has been narrated by Abdullah b. Mughaffal by another chain of transmitters, but with this variation that he (the Holy Prophet) said at the fourth time:" He who wishes (may do to)."