One of the most persistent but baseless myths concerning the third Holy Temple is that it will miraculously descend from the heavens, ready to go, no assembly necessary! Where did this unfounded idea originate, and why? It has absolutely no basis in Torah, whatsoever. "Build Me a sanctuary" (Exodus 25:8) means just that: we are commanded to build for G-d a Holy Temple. Like every Torah commandment it is up to the nation of Israel to do. G-d doesn't do our commandments for us!
During to Hanukah period the Hasmonean cleaned and rebuilt the Temple and temple vessels. After 1967 when Israel liberated the Old City of Jerusalem and the Temple Mount we are required to rebuilt the Temple. We need faith to rebuilt the Temple today just like we built the Temple in Jerusalem and the Mishkan in the Desert.