Sunan an-Nasa'i 652
سنن النسائي#652Sahihأَخْبَرَنَا سُوَيْدٌ، قَالَ حَدَّثَنَا عَبْدُ اللَّهِ، عَنْ يُونُسَ بْنِ أَبِي إِسْحَاقَ، عَنْ مُحَارِبِ بْنِ دِثَارٍ، قَالَ حَدَّثَنِي الأَسْوَدُ بْنُ يَزِيدَ، عَنْ أَبِي مَحْذُورَةَ، أَنَّ آخِرَ الأَذَانِ، لاَ إِلَهَ إِلاَّ اللَّهُ .
It was narrated that Muharib bin Dithar said:"Al-Aswad bin Yazid narrated to me from Abu Mahdhurah that the final words of the Adhan are: 'La ilaha illahha (there is none worthy of worship except Allah)
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Abu GhuddahSahih Isnaad
Al-AlbaniSahih Isnaad
Zubair Ali ZaiIsnaad Sahih
In-book reference: 7:27