There is a concept mentioned in connection with the third Temple that it is going to be completely (or permanently) eternal (for example: Pesachim 88a following Chiddushei Aggadot Maharsha and Rashi to Chullin 91b and Zohar to parshat Pinchas 221a, section 148-149), Zohar 1:28a, Tikkunei Zohar, Tikkun 8 and Sefer HaMa'amarim Meluket, vol. 4, parshat Mattot-Masei. This is often associated with the phrase You bring them in and plant them in the mountain of Your inheritance, the place, HaShem, which You have made for You to dwell in, the Mikdash, HaShem, which Your hands have established. (Shemot 15:17)
This quality distinguishes the third Temple from both the first Temple, whose sanctity (קדושה) was eternal by most opinions, which means that its sanctity remains to this day and the second Temple, which is on a lower level than even the first Temple.
What is this quality of the third Temple and how is it acquired according to the plain sense of things?