All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger.
The statement in reference was quoted by Shaykh Al-Islam Ibn Taymiyyah from 'Uthmaan ibn Saʻeed Ad-Daarimi, and these were not his own words. Shaykh Ibn Taymiyyah said in his book Bayaan Talbees Al-Jahmiyyah:
"‘Uthmaan ibn Saʻeed Ad-Daarimi said in refutation of Al-Mareesi and his companion, 'Stranger than all this is the analogy you make to determine the size of Allah by measuring the Throne in terms of weight and volume, claiming like a blind boy that if Allah was bigger, smaller, or the same size as the Throne ... Had Allah willed, He would have settled on the back of a mosquito and it (the mosquito) would have found Him light (or it would have carried Him on its back) by His power and the subtlety of His Lordship. How then would it be on a magnificent Throne bigger than the heavens and earth..."
It is clear from this quotation that Ad-Daarimi intended by his statement to underline that Allah, the Exalted, is in no need of the Throne or anything else; rather, He is in no need of the worlds and there is no doubt that He is All-Powerful and nothing can challenge Him in the earth or heavens. However, we believe that making such a statement "Had Allah willed, He would have settled on the back of a mosquito" should be avoided and the debate does not need it.
We noticed that the past questions of our dear brother revolve around the blameworthy delving into the matters of ‘Aqeedah (creed) and asking about allegations and doubtful matters and obsessive whisperings regarding Kufr (disbelief). So we advise the brother to fear Allah and refrain from asking such questions and to ask instead about matters that lead to doing good deeds along with seeking knowledge in the correct manner.
Allah knows best.