That you may approve things that are excellent; that you may be sincere and without offense till the day of Christ.
are words closely connected. "Sincere" seems to be an allusion to a practice common then and now. In the bazaars in the East goods are stored away in very obscure places, and persons go in to make their purchases, and purchase them in that dull light. Those who wish to know the matter thoroughly take the goods to the open space where the sunbeam plays, and then, under the full blaze of the light, if no flaw, and if no stain shall be revealed, the article is pronounced "sincere" in the sense of the text, and consequently without offence. He that walks in darkness knows not where he is going. He strikes against this, and he strikes against that, and he cannot understand it. He gets bewildered and ultimately overthrown.
Parallel VersesKJV: That ye may approve things that are excellent; that ye may be sincere and without offence till the day of Christ;