Imam al-Shafi'i (may Allah have mercy on him) said: "A rightly guided imam, Sayyiduna Uthman bin Affan (may Allah be pleased with him), fixed a stipend for the muezzins." And he cited as evidence for the permissibility of taking a wage for teaching good the hadith we have narrated in the Book of the Dowry from the Prophet (peace and blessings be upon him), that he (peace and blessings be upon him) married a woman (to a man) in return for (teaching her) a surah of the Qur'an.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / Q2019