The last instruction the Prophet ﷺ gave me was that I should not appoint a muezzin who takes payment for the call to prayer.
حدثنا أبو بكر بن أبي شيبة حدثنا حفص بن غياث عن أشعث عن الحسن
كان آخر ما عهد إلي النبي ﷺ أن لا أتخذ مؤذنا يأخذ على الأذان أجرا
[Sahih]. Narrated by Tirmidhi, Prayer, chapter on the dislike of the muezzin taking payment for the adhan, hadith no. 209, from the report of Ashath bin Abdul-Malik Humrani with this wording, and he said, hasan sahih. It has corroborating narrations in Abu Dawud, hadith no. 531, and elsewhere.