I have a bunch of co-workers that say they're big-time "christains" but they're constantly spreading rumors. I'd like to challenge them with something from the bible. Thank you!

Rumors fall under the category of gossip and the bible has a lot to say about it.

First you could simply quote The Ninth Commandment:
"You shall not bear false witness against your neighbor."

If that doesn't shut them up, here are a few choice quotes:

Matthew 7:12 – “So in everything, do to others what you would have them do to you, for this sums up the Law and the Prophets.”

Ephesians 4:29 – “Do 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.”

Matthew 7:1 – “Do not judge, or you too will be judged.”

Proverbs 11:13 – “A gossip betrays a confidence, but a trustworthy man keeps a secret.”

Romans 1:29 – “They have become filled with every kind of wickedness, evil, greed and depravity. They are full of envy, murder, strife, deceit and malice. They are gossips.”

Good luck!

Thank you so much! This helps me out a lot!

Try Luke 3:37-38

And of course we all have sin and all still sin daily in many ways, just because we sin, does not mean we are not a Christian, it only means we are not perfected yet as we will when we go to live with the Father.