With what does the caller to Allah begin his call to Allah?

The Shaykh : So, if there are, for example, ten of these people who are enthusiastic about conveying the call of Allah, truly only one of them is worthy of being a caller, because one who lacks something cannot give it. This is a self-evident truth. So if there is among these ten one who is qualified to be a caller to Allah, just as the Messenger of Allah (peace and blessings be upon him) said to Mu'adh ibn Jabal when he called him, when he sent him to call the people, he said to him: And so on. Now, in this departure, we find another violation, and the speech leads to another, and as they say, the matter has many threads. Every caller should be knowledgeable of the Book and the Sunnah, and he should send out two or three who distribute themselves among the community to convey the message to the people. It is obligatory for them to begin with what the Messenger of Allah (peace and blessings be upon him and his family) began with.