The Perfection of Energy - A controlling faculty & a power

According to the “Expositor” in the same section, the characteristic of viriya is the state of a courageous or energetic person, or the action of a courageous person. When viriya arises one is not inert or lax.
One person may be courageous whereas someone else may be a coward. According to the Abhidhamma, also a coward must have viriya, energy, for cowardice. However, in the case of a courageous person the characteristic of viriya appears clearly since he must strive to accomplish something, inspite of obstacles or dangers. Such courage is the characteristic of viriya cetasika. When viriya goes together with the development of kusala, it can become a controlling faculty, the indriya of viriya. The indriya of viriya that arises together with the other indriyas, the indriyas of confidence (saddha), sati, samadhi (concentration) and panna when satipatthana is being developed, is right effort of the eightfold Path, sammavayama. It is right effort for awareness and understanding of the characteristics of realities, just as they naturally appear at this moment.
When panna has further developed, viriya becomes a power, bala, which is unshakable, so that there is energy for awareness and understanding of the characteristics of nama and rupa in whatever situation. One will not be inclined to think that there cannot be awareness of nama and rupa at this moment.
We can investigate the characteristic of viriya when we read the following explanation of the “Expositor” about the controlling faculty, the indriya, of viriya:

“Viriya is the state of a courageous or energetic man,

or it is the action of the energetic,

or it is that which should be effected,

carried out by method or suitable means.

From its overcoming idleness it is a controlling faculty (indriya) in the sense of predominance...

Its characteristic is strengthening or support.”
When viriya arises, someone has the courage to speak, to say what is right, or to act in a wholesome way, not being afraid of trouble, difficulties, or even of losing possessions and becoming poor. This is the characteristic of viriya. Or someone has the courage to explain with regard to the Dhamma the causes which bring their appropriate effects, without paying attention to the fact that he will not be liked by foolish people, or that others will have wrong understanding of his good intention. Someone who is courageous will do what is right with regard to worldly matters as well as Dhamma, because Dhamma is Dhamma: it cannot be changed, it is the truth.