Bukayr bin Amir narrates from Amir (may Allah have mercy on him) that Utbah bin Farqad (may Allah be pleased with him) bought kharaj land, then came and informed Sayyiduna Umar (may Allah be pleased with him). He asked: From whom did you buy it? He said: From its owners. He said: These (the Muslims) are its owners. (Then he asked the Muslims:) Did you sell him anything? They said: No. He said: Go and take your money back.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18410