The phenomenon you're referring to is known as "incorruptibility" or "non-decay" of certain bodies of saints in some religious traditions. It is considered a miraculous occurrence by those who believe in it. From a scientific perspective, however, there is no conclusive evidence to support the claim that these bodies do not decompose.
In many cases, the preservation of these bodies can be attributed to natural processes such as mummification, environmental conditions, or deliberate preservation techniques. Factors such as low temperature, dryness, embalming, or the presence of particular minerals in the soil can slow down decomposition or mummify a body.
It's worth noting that not all bodies claimed to be incorruptible show the same degree of preservation. In some cases, the bodies may undergo partial decomposition while still exhibiting signs of preservation. Additionally, the preservation of a body does not necessarily indicate a supernatural occurrence; rather, it often requires a detailed scientific analysis to determine the causes.
While these cases are considered remarkable by some, they are not considered scientific evidence for the existence of miracles or supernatural intervention. Scientific investigation aims to understand phenomena through natural explanations based on empirical evidence and reproducible experimentation. The question of supernatural or miraculous events falls outside the realm of scientific inquiry and lies in the domain of personal beliefs, faith, and religious interpretations.