He that has light within his own clear breast, May sit i the centre, and enjoy bright day; But he that hides a dark soul and foul thoughts, Benighted walks under the mid-day sun: Himself is his own dungeon. Milton.Comus, Line 381.
There is that which one can communicate to another, and make himself the richer; as one who imparts a light to another has not therefore less light, but walks henceforth in the light of two torches instead of one. Dr. Trench.Parable of the Ten Virgins, 250. Ed. 9.