Adam Clarke's Commentary on the Bible

Verse 16 (Philippians 2:16)

Holding forth the word of life - An allusion, some think, to those towers which were built at the entrance of harbours, on which fires were kept during the night to direct ships into the port. Genuine Christians, by their holy lives and conversation, are the means of directing others, not only how to escape those dangers to which they are exposed on the tempestuous ocean of human life, but also of leading them into the haven of eternal safety and rest.

That I have not run in vain - This appears to be a part of the same metaphor; and alludes to the case of a weather-beaten mariner who has been long tossed on a tempestuous sea, in hazy weather and dark nights, who has been obliged to run on different tacks, and labor intensely to keep his ship from foundering, but is at last, by the assistance of the luminous fire on the top of the tower, directed safely into port. Live so to glorify God and do good to men, that it shall appear that I have not run and labored in vain for your salvation.

- Adam Clarke's Commentary on the Bible