瑜伽論記 5.362

5.362

怖多所作懈怠眾生者，樂聞略故怖修學多，雖有六度萬行但說三學，以三學名攝一切行，非顯了說故名密意。

Regarding "sentient beings who fear many tasks and are indolent": because they delight in hearing what is concise, they fear cultivating much training. Although there are the six perfections and myriad practices, only the three trainings are taught; because the name of the three trainings subsumes all practices, it is called an implicit intention because it is not an explicit explanation.