In summary, shirk and invoking other than Allāh and setting up a deity besides Him or one who is obeyed and followed besides the Messenger (صلى الله عليه وسلم) is the greatest corruption on the Earth.

And there is no rectification for it and nor its people except that Allāh alone should be the one worshipped, that invocation is for Him alone, not for others and that obedience and adherence is for the Messenger (صلى الله عليه وسلم).

And as for the one besides [the Messenger], his obedience is only obligatory if he commands with obedience to the Messenger (صلى الله عليه وسلم). If he commands with disobedience to [the Messenger], then there is no hearing and no obeying.

For Allāh rectified the Earth by His Messenger (صلى الله عليه وسلم) and by His religion and by commanding with Tawḥīd. He prohibited from causing corruption therein through Shirk and opposition to His Messenger (صلى الله عليه وسلم).

And whoever reflects upon every rectification on the Earth (will find) its cause to be the Tawḥid of Allāh and His worship and obedience to His Messenger. And every evil in the world, every trial, tribulation, drought and subjugation by an enemy and other than that, its cause is opposition to the Messenger (صلى الله عليه وسلم) and calling upon other than Allāh.

And whoever reflects upon this as it truly should be reflected upon, will find this affair to be just like that with respect to himself and also in others both generally and specifically and there is no might nor power except by Allāh.