He will be the chief witness for all the Ambiyaa AS attesting that they conveyed the message of Allah to their Ummats. Allah SWT will make the greatness of his beloved apparent to all of mankind, who in a state of restlessness and anxiety for the reckoning to begin will approach every Nabi to no avail, until they approach Nabi Muhammad (sallallahu alayhi wasallam).
He will then praise Allah SWT with the highest words of praise imaginable for a lengthy period of time, and Allah SWT will begin the reckoning upon his intercession. He will be the first and greatest of intercessors, interceding even for those of his Ummah with no hope of salvation. Many will thus be granted Jannah without punishment, or their punishment lightened to only a brief period. Nabi-e-Kareem (sallallahu alayhi wasallam) becomes pleased and will intercede on behalf of the person who reads the dua after the Adhaan, which mentions 'Maqaam Mahmood' - the unique rank and praised station Allah SWT has reserved for His beloved. Reflecting on his great rank in this world and the Hereafter, will enhance our reverence and love for him, and by following his way of life, Allah SWT will grant honour, position and forgiveness in both worlds.