"Indeed, amount the last (of orders) Messenger of Allah ordered me with was to employ a Mu'adh-dhin who would not take a wage for his Adhan."
إِنَّ مِنْ آخِرِ مَا عَهِدَ إِلَىَّ رَسُولُ اللَّهِ ﷺ أَنِ اتَّخِذْ مُؤَذِّنًا لاَ يَأْخُذُ عَلَى أَذَانِهِ أَجْرًا
"The last instruction that the Messenger of Allah gave to me was that I should not appoint a Mu'adh-dhin who took payment for the Adhan." (sahih)
كَانَ آخِرُ مَا عَهِدَ إِلَىَّ النَّبِيُّ ﷺ أَنْ لاَ أَتَّخِذَ مُؤَذِّنًا يَأْخُذُ عَلَى الأَذَانِ أَجْرًا
[Machine] "It was part of what the Messenger of Allah ﷺ entrusted to me that I do not take any payment for making the call to prayer."
كَانَ مِمَّا «عَهِدَ إِلَيَّ رَسُولُ اللهِ ﷺ أَنْ لَا آخُذَ عَلَى الْأَذَانِ أَجْرًا»
"عَنْ عُثْمَانَ بْنِ أَبِى الْعَاصِى الثَّقفىِّ - ؓ -: كَانَ آخِرُ مَا عَهِدَ إِلَىَّ رَسُولُ اللهِ ﷺ أَنْ أَتَّخِذَ مُؤذِّنًا لا يَأخُذُ عَلَى أَذَانِهِ أَجْرًا".