The inspiration for letting your light so shine before men is in Isaiah's condemnation of the phony, self-absorbed ritual fasts of the house of Jacob

 Let your light so shine before men, that they may see your good works, and glorify your Father which is in heaven. 

-- Matthew 5:16

Feed the hungry,
and help those in trouble.
Then your light will shine out from the darkness,
and the darkness around you will be as bright as noon.

-- Isaiah 58:10

Moreover when ye fast, be not, as the hypocrites, of a sad countenance: for they disfigure their faces, that they may appear unto men to fast. Verily I say unto you, They have their reward. 

-- Matthew 6:16

I am the light of the world, or Ye are the light of the world

Then spake Jesus again unto them, saying, I am the light of the world: he that followeth me shall not walk in darkness, but shall have the light of life. ... As long as I am in the world, I am the light of the world. ... I am come a light into the world, that whosoever believeth on me should not abide in darkness. -- John 8:12; 9:5; 12:46

Ye are the light of the world. A city that is set on an hill cannot be hid. ... Let your light so shine before men, that they may see your good works, and glorify your Father which is in heaven. -- Matthew 5:14, 16

Take heed therefore that the light which is in thee be not darkness. -- Luke 11:35