This body is sustained by food. It depends on food to continue, and without food it doesn’t continue. In the same way, the seven awakening factors are sustained by fuel. They depend on fuel to continue, and without fuel they don’t continue.

And what fuels the arising of the awakening factor of mindfulness, or, when it has arisen, fully develops it? There are things that are grounds for the awakening factor of mindfulness. Frequent rational application of mind to them fuels the arising of the awakening factor of mindfulness, or, when it has arisen, fully develops it.

And what fuels the arising of the awakening factor of investigation of principles, or, when it has arisen, fully develops it? There are qualities that are skillful and unskillful, blameworthy and blameless, inferior and superior, and those with a portion of dark or bright. Frequent rational application of mind to them fuels the arising of the awakening factor of investigation of principles, or, when it has arisen, fully develops it.