Scholars say it is kufr to believe God is flesh and blood. However, the Quran does not say anything about whether God does or does not have flesh and blood. So why do scholars say this? Arent we supposed to neither affirm nor deny something that is not mentioned in the Quran

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 is His slave and Messenger.

Among the firmly established principles in the Quran is that Allah Almighty is One, and that nothing of His creation resembles Him, as in Surah Al-Ikhlas [Quran 112], which equals one-third of the Quran, and in other Chapters.

Allah, Glorified and Exalted be He, is free from any deficiency, even if He has not explicitly stated this in Islamic texts.

Any attribute that is related to the creature is a form of deficiency from which Allah is free, with the evidence of the firm verses that indicate that Allah is One and Perfect, and that he is free from any deficiency or resemblance to the creation.

With regard to the flesh and blood, what indicates that they do not apply to Allah is that Allah Says (what means): {There is nothing like unto Him, and He is the Hearing, the Seeing.} [Quran 42:11] This means that Allah is not of the genre of any creature.

Also, the reason for the revelation of Surah Al-Ikhlas is because of a question from the polytheists about the Lord, whether He is of gold, or silver, or such and such, so Allah revealed this Surah wherein He explained that He is not of the kind of any of the creatures.

Moreover, if He is of flesh and bone –Glorified and Exalted is He –then what applies to flesh and bone would apply to Him as well, such as change, decay, and so on. This inference in included in the evidences of resembling Him, which Allah denied from Himself.

We advise you to ask about the fundamentals of faith and the acts of the heart, and other acts of worship and knowledge that every Muslim needs in his religion, and stay away from investigating deeply the innovated details about the Attributes of Allah as this may lead to unpleasant consequences.

The story of Imam Malik in rebuking the questioner about the method of Istiwaa’ of Allah, and ordering the people to get him out of his circle, is well known –and it is confirmed about him with Tawaatur as stated by Ath-Thahabi.

It is more appropriate for you to study one of the books on the methodology of Ahlus-Sunnah wal-Jama'ah, such as Sharh al-Aqeedah at-Tahawiyyah authored by Ibn Abul-‘Izz, or other books.

You should know that in principle you should abide by what was stated in the Quran and the Sunnah without investigating what is beyond that, as stated by Imam Ahmad, the leader of Ahlus-Sunnah wal-Jamaa'ah:

“Allah should not be described except with whatever He described Himself with, or with whatever the Prophet described Him with; one should not exceed the Quran and the Hadith.” [End of quote]

Allah knows best.