俱舍論疏 8.209

8.209

[On the] Śāstra's [words], "Or even if one does not accept... it is just existence at birth (upapattibhava)": this is the third part, rebuking their confusion over the text. You are confused by the sūtra text. When the sūtra says "without interval one is born", it refers to being born into intermediate existence. Because intermediate existence is the preliminary to birth, it is called "birth". It takes its name from birth, but this is not its specific nature. If speaking of its intrinsic nature, it should be called "arising", as explained at length above.