阿彌陀經疏 1.174

1.174

經曰：「其土眾生聞是音已，皆悉念佛念法念僧」，次第五聞聲動念也，謂聞鳥說法皆生善念念三寶也。

The sūtra says: "When the sentient beings of that land have heard these sounds, they all become mindful of the Buddha, mindful of the Dharma, and mindful of the Saṅgha." Next, the fifth [point] explains hearing the sounds and stirring mindfulness, meaning that upon hearing the birds expound the Dharma, they all give rise to wholesome thoughts and become mindful of the Three Jewels.