Mt 13, 9

"Accordingly, people should be prevented from withdrawing money from the country in the run-up to exit by effectively bottling it up within the domestic economy. In particular, from the announcement of the redenomination until banks were able to distinguish between euro and drachma withdrawals, banks and cash machines would need to be shut down.
The shutdown of ATMs can be administered relatively simply by the ‘switching companies’ that connect the machines to the various networks. The exiting country could simply declare a bank holiday in which all banking transactions, including those conducted electronically, were prevented. One approach would be to make the announcement of departure on a Friday, after the close of business, leaving the weekend, when most banks would be closed anyway, to make the necessary arrangements. But this could not be allowed to be a normal banking weekend as electronic transactions would still need to be prevented and ATMs shut down."

"Leaving the Euro: A Practical Guide"