The hadith of the well of Buda'ah is not a permission to use sewage or visibly filthy water. It teaches a legal rule about ritual purity: a large body of water is not made impure by mere contact with filth unless the impurity affects it.
What critics are rightly worried about
The objection is not silly. If someone imagines a small, stagnant well full of menstrual rags, carcasses, and rotting waste, then saying "use it for wudu and drink it" would be dangerous and contrary to ordinary hygiene. Dirty water can carry disease, even when people do not understand the microbes involved.
So the question is: does the hadith actually say that the Prophet (PBUH) approved using visibly contaminated water, or is that an overreading?
What the report actually establishes
It was said: "O Messenger of Allah, shall we perform wudu from the well of Buda'ah, while menstrual cloths, dead dogs and rotten things are thrown into it?" He said: "Water is pure, and nothing makes it impure."
Sunan Abi Dawud 66; Jami' at-Tirmidhi 66; Sunan an-Nasa'i 326
The report is about whether water becomes ritually impure simply because impurities have fallen into it. The answer is no - not automatically. Classical jurists did not understand this as meaning that water remains pure even when its smell, color, or taste is changed by filth. The settled rule in the schools is that if impurity alters the water, it is not used for purification.
This is why scholars explained the well of Buda'ah as a well with abundant water, not a small bucket of filth. The ugly items mentioned were not necessarily sitting there visibly while people washed from it. They could be things carried into it or cast nearby and washed in, while the water itself remained unchanged. The legal question was about contact, not about drinking putrid water.
Ritual purity is not the same as medical safety
Another confusion is to treat "pure" here as a laboratory claim that water contains no harmful organisms. In fiqh, "tahur" means legally purifying for worship. It is a legal category, not a full medical analysis.
Islam also has a broader rule: harm is to be avoided. The Prophet (PBUH) forbade causing harm and taught cleanliness in many practical ways. If water is known to be harmful, foul, poisoned, contaminated, or likely to spread illness, a person should not drink it or expose people to it. That is not a contradiction of the hadith; it is applying other principles alongside it.
What this hadith does and does not prove
It does prove that a large amount of water is not judged ritually impure merely because some impurity touched it, so long as the water is not changed by that impurity. This is sensible: otherwise almost every natural water source would be unusable, because leaves, animals, soil, and waste may come into contact with it.
It does not prove that Muslims should use water that is visibly filthy, rotten-smelling, disease-ridden, or unsafe. Nor does it claim that ritual purity equals modern potability. The critic's strongest version attacks a picture of the hadith that classical scholarship did not hold.
Read in its legal and historical setting, the report is not a denial of hygiene. It is a practical ruling about purification, limited by the condition of the water and by the wider Islamic duty to avoid harm.