Imaam Ibnul Qayyim (rahimahullaah):

Whoever ponders upon the state of affairs of the world will find that every affair of rectification is due to Tawheed, singling out Allaah in worship and obedience to His Messenger (Muhammad). And every evil in the world, trial, affliction, scarcity (in livelihood), being overpowered by an enemy and other than that is due to (people’s) opposition to the Messenger and (their) call to other than (the way of) Allaah and His Messenger. Whoever truly ponders upon this and examines the state of affairs of the world since its beginning and until the time Allaah will take it away and those upon it, he will realize this affair regarding himself and other than him—in general and specific. And there is no Might or Power except with Allaah –The Most High, The Most Great. [بدائع الفوائد —3/525-526]