How can Allaah will and desire what is not pleasing to Him?

Allah may dislike something, but this does not counter His willing that thing for another purpose as it will be a cause for something that is beloved to Him. For example, Allah created Iblees. He is the being of wickedness in ways of life, actions, beliefs and volitions. He is the cause of many human beings' unhappiness and for their actions that are displeasing to Allah. He is the deliverer of the acts that are in opposition to what Allah loves and is pleased with. At that same time, though, he is a means for many things that Allah will love to bestow on His creatures. Therefore, his existence is more beloved to Allah than his non-existence. This is true for many reasons, including the following:

Firstly, by creating Iblees, Allah demonstrates to His servants His ability to create opposites and contraries. He has created a being that is the most wicked and the cause of every wickedness. Yet, at the same time, He created his opposite, the angel Gabriel. Gabriel is one of the most noble of all creatures and a source of only good. Blessed be the Creator of the latter and the former. Similarly, this power of Allah's is demonstrated in His creation of night and day, disease and cure, life and death, right and wrong, good and evil. This is part of the detailed evidence of His perfect power, absolute authority, dominion and rule, for He has created those opposites. They are set up against one another. He has used them for meeting His goals. If the world were devoid of these opposites, we would not have witnessed the faultless wisdom, the
absolute power and the perfect rule He has over all things.

Secondly, Iblees enables the manifestation of such names (and attributes) of Allah as the Dominant, the Avenger, the Just, the One Who chastises, Who is strict in punishment, Who is quick to judge, Whose grip is strong, Who brings low, and Who humiliates. These names and actions are all part of perfection. Their objects, therefore, have to exist. If the jinns and humans were similar in nature to the angels, none of these names would have become manifest.

Thirdly, Iblees makes possible the manifestation of such names of Allah as show that He forbears, forgives, overlooks and forgoes the violations of His rights, and sets sinners free. If He had not created things which He detests but which makes possible the manifestation of these names, these benefits and wisdom would have been lost. The Prophet (r) referred to this point when he said,

“If you did not sin, Allah would have removed you and put in your place a people who will sin and then ask Him to forgive them that He may forgive them.” (Sahih Muslim, vol. , p. , no. )

Fourthly, Iblees makes possible the manifestation of the wisdom and knowledge of the One Who is wise and knowing, Who places things in their proper places, and nothing in the wrong place, as is dictated by His wisdom and knowledge. He knows to whom He should give His message. He knows who are fit for it and who will receive it gratefully and who are not fit for it. If undesirable causes were removed because they produced evil consequences, the good things that outweigh these evils would have never been realized. Look at the sun, the moon and the wind. They produce good as well as evil but their good greatly outweighs their evil.

Fifthly, if Iblees had not been created, a number of things by which men affirm their servitude to Allah would not have occurred. The act of worship. jihad, is one of the most beloved acts of worship to Allah. If all people were Believers, that act of worship would be nullified as well as its consequences of having loyalty and enmity for the sake of Allaah. Similarly, the worship in the acts of commanding good and eradicating evil, in having patience, in going against one’s desires, in sacrificing out of love for Allah, in
repentance and asking forgiveness, in seeking refuge in Allah from being overtaken by his enemy, and being protected from the evil one's plots, and so on, are all part of the wisdom that the human mind would not have been able to discover (if it had not been for the creation of Iblees).

(Explanation of Aqeedah at-Tahawee by Ibn Abil-‘Izz)