成唯識論述記 3.249

3.249

述曰：諸聖生上，必不下生，變為下土亦何所用。以本變土，本為身用，定不能用，變之何為？此中且舉聖生無色，就顯處說，色界、異地類此亦然。

The Commentary states: When various noble ones are born in the higher [realms], they will definitely not be born below; of what use would transforming into the lower lands be? Since the fundamental transformation of a land is fundamentally for the use of the body, if they definitely cannot use it, why transform it? Here, noble ones being born in the formless realm is cited merely to speak from the most obvious case; the form realm and different stages are likewise analogous to this.