大般涅槃經疏 12.31

12.31

「復次如來常為」下，是品中第十一，答上云何示多頭之問。佛答如來示種種身即是多頭，說種種法即是多舌（云云）。

From "Furthermore, the Tathāgata always for the sake of" onwards is the eleventh [section] within the chapter, answering the preceding question, "How does he show multiple heads?"
The Buddha answers that the Tathāgata's showing various bodies is itself multiple heads, and speaking various dharmas is itself multiple tongues, and so forth.