大乘起信論別記 1.54

1.54

言「初發意菩薩等」者，十解已上三賢菩薩也。十解初心名發心住，是故此中名初發意。

When it says "Bodhisattvas who have newly aroused the intention [for enlightenment], and the like," these are the bodhisattvas of the three grades of sages, from the ten understandings upward. The initial mind of the ten understandings is called the abode of the arousing of the aspiration, and therefore here it is called "newly aroused the intention."