Musnad Ahmed: Hadith 3750

I said: O Messenger of Allah, what act of wrongdoing is worst? He said: "A cubit of land that a Muslim man detracts from what belongs to his brother. There is not even a pebble of land that he takes, but he will be encircled by it on the Day of Resurrection down through the depths of the earth, and no one knows how deep it is except Allah, may He be glorified and exalted, Who created it.”