Houseflies cannot carry food away and they can only feed on liquids. They secret enzymes to break down solids and then suck it as a liquid.
HouseflyHouseflies play an important ecological role in breaking down and recycling organic matter. Adults are mainly carnivorous; their primary food is animal matter, carrion, and faeces, but they also consume milk, sugary substances, and rotting fruit and vegetables. Solid foods are softened with saliva before being sucked up.
Solid foods are broken down by enzymes before being sucked. So whatever a housefly takes is already digested. This was known recently, however this was portrayed in the Quran 1400 years before it was discovered.
٧٣ يَا أَيُّهَا النَّاسُ ضُرِبَ مَثَلٌ فَاسْتَمِعُوا لَهُ ۚ إِنَّ الَّذِينَ تَدْعُونَ مِنْ دُونِ اللَّهِ لَنْ يَخْلُقُوا ذُبَابًا وَلَوِ اجْتَمَعُوا لَهُ ۖ وَإِنْ يَسْلُبْهُمُ الذُّبَابُ شَيْئًا لَا يَسْتَنْقِذُوهُ مِنْهُ ۚ ضَعُفَ الطَّالِبُ وَالْمَطْلُوبُ
"Weak are the pursuer and the pursued" The pursuer is weak because he is missing what the housefly stole. But it also says that the perused, that is whatever the housefly took, is also weak. Today we know why it is weak, because it is already digested.
How could an illiterate man who lived 1400 years ago have known that whatever a housefly takes is already weakened?
The Quran (Koran, the book of Islam) contains scientific knowledge that could not have been known 1400 years ago. It ranges from basic arithmetics to the most advanced topics in astrophysics. You are invited to go through those miracles and judge for yourself.