1 Gita Sloka Every Day - Chapter 14 - Gunatraya Vibhaga Yoga - Sloka 11

The entire content of this mail is from Swami Adidevananda's translation of Ramanuja's  Gita  Bhashya and Swami Chidbhavananda's Bhagavad Gita, both published by Ramakrishna Mission

The ways of the three gunas are now explained

The Symptoms of the Gunas 11-18

1 Gita Sloka  Every Day - Chapter 14 - Gunatraya Vibhaga Yoga - Sloka 11

Sanjaya reporting the Kurukshetra War to Dhritarashtra

Sarva dwareshu dehe asmin prakashah upajayate I

Gyanam yada tada vidyat vivrudham sattvam iti ute II sloka 11

When the light of knowledge beams through all the gateways of the body, then it may be known that sattva is predominant. 

If a lamp is placed within a box fitted with glasses of various hues, its light shines through all the glasses. The intensity of the light adds to the brilliance pouring out. man's body is very much like that  box. The sense organs are the gateways for the light of the self within, to beam into view. While in sattva, the effulgence of the self is at its height. And this is evinced by the functioning of the senses. In the act of seeing there is sharpness, in hearing there is alertness, in performing an action, there is precision, accompanied by deliberation and accuracy. All the senses function pleasantly at their best. These are the marks of the predominance of sattva.