Philippians 2:14-16 (NIV)
14Do everything without complaining or arguing,
15so that you may become blameless and pure, children of God without fault in a crooked and depraved generation, in which you shine like stars in the universe
16as you hold out the word of life--in order that I may boast on the day of Christ that I did not run or labor for nothing.
James 5:9 (NIV)
9Don't grumble against each other, brothers, or you will be judged. The Judge is standing at the door!
Ephesians 4:29 (NIV)
29Do not let any unwholesome talk come out of your mouths, but only what is helpful for building others up according to their needs, that it may benefit those who listen.