Saying “Remember Allah” or “Send Blessings on the Prophet” to Draw Attention
Question

Is it permissible to make people be quiet when they are talking by saying the following: “O people, remember Allah” or “Send blessings upon your Prophet”? For example, among us -- according to some tribal customs -- if a person wants to address one of the guests when people who are still talking amongst themselves, he says, “O people, send blessings upon your Prophet” or “Remember Allah,” then everyone falls silent, then he starts saying what he wants to say.
I heard one of the preachers at Jumu’ah (Friday) prayers say that it is not permissible to ask people to be quiet by saying “Send blessings upon your Prophet,” and it is not permissible to use this phrase to make people be quiet.
Praise be to Allah.It seems that there is nothing wrong with getting people's attention by saying “Remember Allah” or “Send blessings upon your Prophet (peace and blessings of Allah be upon him). 
Al-Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said: 
Some of our scholars, when they want to say something or give an exhortation from time to time, stand up and say: “Send blessings upon the Messenger of Allah,” then they speak briefly. Then they say to them after that, “Send blessings upon the Messenger of Allah.” 
Was this narrated from the Messenger (peace and blessings of Allah be upon him)? 
He replied: 
What was narrated from the Prophet (peace and blessings of Allah be upon him) in sermons and speeches was that he would start by praising Allah, but there is nothing wrong with a person sending blessings upon the Prophet (peace and blessings of Allah be upon him) after that. So he may recite the Shahadah (testimony of faith) and say: Ashhadu an la ilaha ill-Allah wa ashhadu anna Muhammadan ‘Abduhu wa Rasooluhu (I bear witness that there is no god but Allah and I bear witness that Muhammad is His slave and His messenger), and send blessings upon the Prophet (peace and blessings of Allah be upon him) then say, Amma ba’d (to proceed), and start on the topic of his speech. 
But some khateebs (orators), when they see that the people are not paying attention, tell them, “Say, La ilaha ill-Allah” or “Remember Allah.” And some of them say, “Send blessings upon the Prophet (peace and blessings of Allah be upon him),” intending thereby to get the people's attention. And some of them say, “Pay attention and listen,” and so on. 
It seems to me that those who say this during the khutbah (sermon) do not intend that the listeners should do this act of worship; rather their aim is to get the attention of their audience. 
I do not think that there is anything wrong with this, in sha Allah. End quote. 
Fatawa Noor ‘ala al-Darb (Fatawa Mutafarriqah/ al-da’wah wa’l-Amr bi’l-Ma’roof wa’l-Nahy ‘an al-Munkar)
And Allah knows best.