Charles Ellicott Commentary Jeremiah 32:11

"So I took the deed of the purchase, both that which was sealed, [according to] the law and custom, and that which was open:" — Jeremiah 32:11 (ASV)

Both that which was sealed ... and that which was open. —We can only speculate why there were two documents, and why one was sealed and the other open. Possibly, as in modern transactions, one was simply a duplicate copy of the other; the sealed document was the formal evidence of purchase kept by the buyer, and the other was left with the vendor for reference.

The more probable explanation, however, is that the unsealed document, which the witnesses did not sign or see, contained details that did not concern the witnesses: the price paid (though the mention of the witnesses before the weighing of the money argues against this view), the conditions of resumption by the vendor, and possibly some reference to the period of seventy years, at the end of which, and not before, Jeremiah’s heirs might expect to take possession.

According to the law and custom. —Better, that is, the agreement and the conditions. The whole transaction may be compared, as an example of ancient conveyancing, with the transfer of the field and cave of Machpelah in Genesis 23.