The Ruling on the Mu'aththin saying: "Pray, may Allah guide you" in a raised voice after the Athan

Question :

Q Some Mu'aththins, after calling the Athan, and before making the prescribed supplication, say in the microphone: "Pray, may Allah guide you." What is the ruling on this?

Answer:

Allah, the Most High says:
This day I have perfected your religion for you, completed My Favor upon you, and have chosen Islam for you as your religion.

And the Prophet said:
"Adhere to my Sunnah and that of the righteous, Well- Guided Caliphs - hold fast to it and cling to it by your molar teeth; beware of newly invented matters, for every newly invented matter is an innovation and every innovation is a misguidance.

He also said:
"Whoever innovates in this matter of ours that which is not from it will have it (his innovation) rejected.

And it has been reported from one of the righteous Salaf that he said:
"Follow and do not innovate and that will be sufficient for you." Based on this, it is incumbent upon the Muslim in matters of worship to confine himself to what has been authentically legislated and not to add anything to it, by claiming that it is a good deed, for if there were any good in it, the Prophet would have informed us about it, and he would have done it, and his Companions, may Allah be pleased with them, would have done it during his lifetime and afterwards. From this, the answer to the (above) question is clear, which is that it is necessary to restrict oneself in the Athan to what has been authentically legislated regarding the description of the Athan, and that adding anything to it is a form of innovation. And Allah knows best.

Source:
The Permanent Committee
Fatawa Islamiyah, Vol. 2 Pages 131-132