yatkṛtakaṁ tadānityam (what was created will be destroyed)
All that is created will be eventually destroyed.
This concise statement points out the difference between matter and spirit. The objects of the material world are in time subject to creation and destruction. The world itself is subject to creation and destruction. Our body, family, friends, countries, gadgets we use, everything is subject to creation and destruction. Once understanding this fact, a thoughtful man naturally accepts that, as the opposite, there must be a thing that is not subject to creation and destruction, a thing that is eternal, of which temporary is reflection. That is spirit. This spirit has three parts; living God, innumerable spiritual souls, and the spiritual world. It is a faulty conclusion, strictly under the confinement of material logic, to consider spirit force to have the same curse to be created and destroyed in time. Time is just another manifestation of the material sphere. It has no dominion over the spiritual world and its inhabitants. Inhabitants, families, friends, planetary regions of the spiritual world stay as they are, ever-expanding in the bliss of pleasure pastimes with Śré Hari.
The material world is not an illusion, as proposed by many false spiritualists. It has its real cause and effect but for some time only, short or long, whatever is the case. Stubborn living entities are repeatedly injected into the womb of material energy, due to turning their backs on the servitude principle to the Lord granting them full relaxation from the marry-go-round of creation and destruction.