[Sale of Undivided (Common) Land]

Question: A man sold 100 “ḥabala” (measured plots) out of a tract he co-owned with others; the thing sold was an undivided share (mushāʿ), not yet partitioned. He only sold because he needed the cash. The buyer purchased and gave the seller a guarantor for the price; the seller received one-tenth of the price. Then the guarantor and the buyer stalled. More than ten years passed and the seller received nothing further. After those ten years the land had become expensive—its price rose to more than ten times. The seller then disavowed the sale, returned what he had received, and insisted on holding to his land. A dispute arose. The buyer said, “I fulfilled [my duty] by giving you a guarantor,” and produced the guaranty document. The seller replied, “I sold only out of need for the price, and I never got the price.” The buyer said he had already resold that land. The sale had been in “white land” (open, unimproved right) that was later allotted by head-count (al-d ak r). How should this case be resolved?