Kāyasutta

sn46.2:10.1 And what fuels the arising of the awakening factor of investigation of principles, or, when it has arisen, fully develops it?

sn46.2:10.2 There are qualities that are skillful and unskillful, blameworthy and blameless, inferior and superior, and those with a portion of dark or bright.

sn46.2:10.3 Frequent rational application of mind to them

sn46.2:10.4 fuels the arising of the awakening factor of investigation of principles, or, when it has arisen, fully develops it.