As recorded in al-Jami and al Jawahir, our Shaikh Ahmad Tijani (may Allah be pleased with him) said: "You should know that the Prophet used to impose the general rules on the common folk during his lifetime; that is to say, when he declared something unlawful, he declared it unlawful for everybody, and when he prescribed something, he prescribed it for everybody, and likewise in the case of all the obvious rules of the Sacred Law.
In addition to all that, he used to impose special rules on the elite, and he used to assign certain matters to some of his Companions but not to others, as is well known and thoroughly recorded in his traditional reports. When he was transferred to the abode of the Herafter, the situation was therefore the same as it had been during his life in this world.
He had begun to entrust to his Cummunity the special decree imposed on the elite, but not modification of the general decree imposed on the common folk, so modification thereof ceased with his death, while his gracious favor continued to apply to the special degree imposed on the elite. If anyone imagines that all of his support for his Community came to an end with his death, as in the case of all other dead men ,he is ignorant of the Prophet’s degree and guilty of treating him with indecently. He is also in danger of dying as an unbeliever, if he does not repent of this deluded conviction.."
end of quote.
So in a nutshell this means that the Prophet is not a dead man that only came in this world and has no access to it anymore.
The Prophet is the key to all that exists, therefore his support and teachings to his ummah are still active from the past, today, and until the day of judgement. The Prophet is still teaching the awliya Allah and the people of knowledge. And through him these awliya learn various awrad and azkar. All of them are from the Quran in various ways.
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It's a high maqam to be humble and open minded about Allah's servants. It is better to see someone as a wali and in reality they are a hypocrite, rather than see someone as a hyprocrite but in reality they are a wali of Allah.-Shaykh Hasan Cisse