"Do all things without murmurings and disputings: That ye may be blameless and harmless, the sons of God, without rebuke, in the midst of a crooked and perverse nation, among whom ye shine as lights in the world." (Philippians 2:14-15)
The Holy Spirit makes sure that we do not take lightly the obligation to live godly lives. This "list" contains both warnings and promises.
Everything is to be done without "murmurings" and "disputings." Both words are very interesting synonyms of heart attitudes that produce ungodly behavior. The Greek word translated "murmur" is goggusmos, and it is almost an onomatopoeia (sounds like what it actually is)--a secret debate, muttering to oneself. The "dispute" (Greek dialogismos) suggests a logical debate with oneself.
We are commanded to excise that kind of behavior from ourselves so that we may well be blameless and harmless as the "sons of God," living "without rebuke." These words are powerful in their description of God's expectations for us.
The blameless condition is first an eternal promise that comes with salvation: "To the end he may stablish your hearts unblameable in holiness before God" (1 Thessalonians 3:13). That condition "works out" in this life as a faultless reputation that is harmless. Paul uses the term this way: "I would have you wise unto that which is good, and simple concerning evil" (Romans 16:19).
Finally, if we eliminate "murmuring and disputings" from our inner thoughts and actively seek to be "blameless and harmless" with our external behavior, we will be "without rebuke" in the middle of this sadly sinful world. "Be diligent that ye may be found of him in peace, without spot, and blameless" (2 Peter 3:14). HMM III