俱舍論頌疏論本 9.11

9.11

無對者，第四無礙門，對謂對礙，中有凌空，金剛山等所不能遮，故名無對。曾聞析破炎赤鐵團，見有生蟲故。不可轉者，第五不可轉門，謂五趣中有不可轉也。人中有起但往人趣，必不可令人中有沒，餘中有起，天等亦然。

Regarding "unobstructed", this is the fourth topic, on lack of hindrance. "Obstructed" means resistant hindrance; the intermediate existence moves through the air, and even the Vajra mountains and the like cannot block it, hence it is called "unobstructed". It was once heard that upon splitting open a glowing red-hot lump of iron, living worms were seen within it. Regarding "unalterable", this is the fifth topic, on being unalterable, meaning that the intermediate existence of the five destinies cannot be altered. When a human intermediate existence has arisen, it only goes to the human destiny; it can never be made to perish as a human intermediate existence and arise as another intermediate existence; the same holds for celestials and the rest.