Quran 24:11-17

Those who have brought forth the false accusation were a group from within you.  Do not think it is bad for you, for it is good for you. Every person amongst them will have what he deserves of the sin.  And as for he who had the greatest portion of it, he will have a great retribution.

If only when you heard it the believing men and women should have thought good of their own selves and said: "This is an obvious lie!"

If only they had brought four witnesses to it.  If they did not have the witnesses, then these with God are the liars.

And had it not been for God's favor upon you and His mercy upon you in this world and the Hereafter, a great retribution would have touched you for what you had spoken.

For you have cast it with your tounges, and you say with your mouths what you have no knowledge of, and you think it is a minor issue, while with God it was great.

And when you heard it you should have said: "It was not right for us to speak of this. Glory to You, this is a great lie."

God warns you not to repeat something similar to this ever, if you are believers.