Making Remembrance Aloud after the Athan

Question :

Some Mu'aththins in certain Muslim countries say after the Athan: "O Allah! Send prayers upon our Master, Muhammad and upon all his family and Companions." Is there any objection to this? Please advise me.

Answer:

This position requires clarification: If the Mu'aththin says this in a low voice, then it is lawful for the Mu'aththin and for the others who respond to the Athan because the Prophet said:
"If you hear the Athan, say what the Mu'aththin says, then invoke prayers on me, for whoever invokes prayers on me once, Allah sends ten prayers on him because of it. Then ask Allah to make me an intercessor, for it is a station in Paradise which is not fitting for any but a slave from among the slaves of Allah, and I hope that I will be he; so whoever asks for intercession for me, (my) intercession will permitted for him.

Al-Bukhari narrated in his Sahih, on the authority of Jabir bin 'Abdullah, may Allah be pleased with him, that he said: Allah's Messenger said:
"Whoever said, when he heard the call (to prayer): "O Allah! Lord of this perfect supplication and the established prayer, grant Muhammad intercession and a virtuous place and raise him to a praiseworthy position as You have promised him." - will have my intercession made permissible for him on the Day of Resurrection.

But if the Mu'aththin says this in a loud voice like the Athan, then it is an innovation. His doing so would make it seem as if it is a part of the Athan, and it is not permissible to add anything to it, because the end of the Athan is the saying: La ilaha illallah (None has the right to be worshipped except Allah) and it is not allowed to add anything to this. If this was good, the righteous Salaf would have done it before; indeed, the Prophet would have commanded his people to do it and legislated it for them. And he said:
"Whoever performs a deed which is not from this matter of ours, he will have it rejected".

I ask Allah, the Most Glorified that he increase us, you, and all of our brothers in knowledge of His Deen (religion), and that He bless us all with firmness in it. Verily, He is All-Hearing, Ever Near (to all things).

Source:
Ibn Baz
Fatawa Islamiyah, Vol. 2 Pages 138-129