That is the power of Ojas.

The Yogis claim that of all the energies that are in the human body the highest is what they call “Ojas”. Now this Ojas is stored up in the brain, and the more Ojas is in a man’s head, the more powerful he is, the more intellectual, the more spiritually strong. One man may speak beautiful language and beautiful thought, but they do not impress people; another man speaks neither beautiful language nor beautiful thoughts, yet his words charm. Every movement of his is powerful. That is the power of Ojas. (CW V1. 169.)