Albert Barnes on Matthew 5:15

Neither do men light a candle, etc. Jesus proceeded here to show them that the very reason why they were enlightened was, that others might also see the light, and be benefited by it. When men light a candle, they do not conceal the light, but place it where it may be of use. So it is with religion. It is given that we may benefit others. It is not to be concealed, but suffered to show itself, and to shed light on a surrounding wicked world.

A bushel. Greek, a measure containing nearly a peck. It denotes anything, here, that might conceal the light.

(1) "bushel" or, "The word, in the original, signifieth a measuring containing about a pint less than a peck."