觀無量壽佛經疏 3.111

3.111

十、從此想成時下，至憶持不捨已來，正明因定得見極樂莊嚴。又聞一切莊嚴皆能說於妙法，既見聞此已，恒持莫失，名守定心也。

Tenth, from "When this visualization is accomplished" down to "recollecting and maintaining it without abandoning it," it properly explains that due to concentration one comes to see the adornments of Sukhāvatī. Furthermore, one hears all the adornments capable of expounding the wondrous Dharma; having seen and heard this, constantly maintaining it without losing it is called preserving the mind of concentration.