مِشْكَاةُ الْمَصَابِيحِ
Mishkat al-Masabih 662
Prayer
The Excellence of the Adhan and the Response to the Mu’adhdhin - Section 1
وَعَنْ عَبْدِ اللَّهِ بْنِ مُغَفَّلٍ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «بَيْنَ كُلِّ أَذَانَيْنِ صَلَاةٌ بَيْنَ كُلِّ أَذَانَيْنِ صَلَاةٌ» ثُمَّ قَالَ فِي الثَّالِثَةِ «لِمَنْ شَاءَ»
‘Abdallah b. Mughaffal reported God’s Messenger as saying, “Between every pair of adhans there is a prayer; between every pair of adhans there is a prayer.” Then he said on repeating it a third time, “for him who wishes.” (Bukhari and Muslim.)
Mishkat al-Masabih, 662مُتَّفَقٌ عَلَيْهِ (الألباني)