It is narrated from Sayyiduna Miswar bin Makhramah (may Allah be pleased with him); he said: I heard the Prophet (peace and blessings be upon him) say: "Whoever takes any part of the land (unjustly), it will be hung around his neck as a collar of seven earths on the Day of Resurrection."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 17167