Three boxes of head tefillin, measuring together about 1,000 liters, were recovered from the victims of Bethar.If one acquires a plot of land from an oppressor and then acquires it from the owner (by paying him required ¼ of the amount), it is not
valid.
He has to acquire it from the owner, and then from the oppressor. The
owner's sale needs to be recorded in a document with title insurance.
Then we assume that the owner was sincere.Similarly, a buyer of a field designated for ketubah should acquire consent from the wife and the field from the husband.