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From quite early, then, the Temple administrators developed the habit of advancing goods to local merchants – some of them private, others themselves Temple functionaries – who would then go off and sell it overseas… Before long, we find not only commercial loans, but also consumer loans – usury in the classical sense of the term. By c. 2400 BCE it already appears to have been common practice on the part of local officials, or wealthy merchants, to advance loans to peasants who were in financial trouble on collateral and begin to appropriate their possessions if they were unable to pay…

We have already had occasion to note the predominance of credit money in Mesopotamia, the earliest urban civilization that we know about. In the great temple and palace complexes, not only did money serve largely as an accounting measure rather than physically changing hands, merchants and tradespeople developed credit arrangements of their own. Most of these took the physical form of clay tablets, inscribed with some obligation of future payment, that were then sealed inside clay envelopes and marked with the borrower’s seal. The creditor would keep the envelope as a surety, and it would be broken on repayment. In some times or places, at least, these bullae appear to have become what we would now call negotiable instruments, since the table inside did not simply record a promise to pay the original lender, but was designated “to the bearer” – in other words, a tablet recording a debt of five shekels of silver (at prevailing rates of interest) could circulate as the equivalent of a five-shekel promissory note – that is, as money.

– Graeber, Debt