金光明最勝王經疏 4.303

4.303

解妨者，問：經云「持此總持者具大福德，已多佛所殖善持戒，決定能入甚深法門。」既云已多佛所殖善持戒，此即自能恒覩諸佛，何假佛教總持之法？答：更令增進，故教神呪。

Regarding resolving doubts: Question: The sūtra states, "One who upholds this dhāraṇī possesses great merit, has planted [good roots] and upheld the precepts in the presence of many buddhas, and is definitely able to enter the profound Dharma-gate." If it is said that one has already planted [good roots] and upheld the precepts in the presence of many buddhas, this person should already be able of themselves constantly to behold all buddhas; why rely on the Buddha to teach the method of the dhāraṇī? Answer: To cause them to advance further, he therefore teaches the divine mantra.