As the Most High says:

“There has certainly come to you a Messenger from among yourselves; your hardship weighs heavily upon him; he is concerned for you; and to the believers he is compassionate and merciful.” (Repentance 9:128)

He also says:

“The wife of the governor said, ‘Now the truth has become manifest: it was I who sought to seduce him.’” (Joseph 12:51)

And He says:

“To God belongs all might, and to His Messenger, and to the believers.” (The Hypocrites 63:8)

He further says:

“She possesses a magnificent throne.” (The Ant 27:23)

And He says:

“Thus does God seal the heart of every arrogant tyrant.” (Ghafir 40:35)

And He says:

“Beyond them was a king.” (The Cave 18:79)

There are many other verses of the same kind.

Now, when a created being is described as merciful, mighty, possessed of mercy and might, great, compelling, proud, and the like, you have ascribed to him qualities and relational attributes, and you have attached to him something that other creatures may also be labeled with—whether by spoken word or inner conviction.

Given this, your position must be either self-contradictory—therefore invalid, and indeed it is so in reality, for such people inevitably speak of God with terms that carry real meanings, thereby contradicting their claim of pure abstraction and total negation—or you must say that the matters you affirm for Him are unlike those affirmed for created beings. In that case, you have arrived at the very response upheld by the people of affirmation (ahl al-ithbāt).