大毘盧遮那經供養次第法疏 2.56

2.56

二、來意者，前品之中依於法則持誦，誦者必有真言事業，故此品中來。

Second, the purpose of inclusion: in the previous chapter, recitation was practiced according to the ritual rules; one who recites will inevitably perform mantra operations, hence this chapter follows.