Ezekiel 44:31

“The priests shall not eat of anything which dies of itself, or is torn, whether it be beast or bird.”

This was in fact true for all Israelites (Leviticus 7:24), but it is emphatically stressed here that it is especially important for priests. Clearly such animals may have died of disease, or have become infected. But the main point ritually was that they had not been killed cleanly and the blood properly dealt with.

These renewed instructions to the priests were necessary so that when the return from exile took place they would immediately be aware of the need to return to the Law of Moses, and even to go beyond it in being holy before God. What had previously applied only to the High Priest now applied to all priests. For they served a holy God, and had to be a lesson and example to the people.

The assumption is that first a sanctuary would be set up, and then a temple built, which would mirror to some extent the heavenly temple. But only the former is commanded (Ezekiel 43:18). And however mean and crude their temple might be they would be ever aware of the glory of the heavenly temple that it represented. For they were the people of Yahweh, and Yahweh was glorious and holy above all things. Thus they need never be ashamed of their temple however simple it was, because of what it represented.