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If you are transferring i.e. not arriving or departing from Hamad Intl. Airport; you are allowed to carry alcohol with you. The limit is 5 ltr. per person.
You will not be allowed to leave the airport with the alcohol.
Please read
As a transfer passenger you may carry alcoholic beverages in your baggage. However these must be packed in containers of less than 5 litres.
Please note if you intend to exit the airport and visit Qatar before continuing your journey, then alcoholic beverages cannot be brought into the country under any circumstances. These will be confiscated and you wonβt be able to retrieve them at any time.
If youβre travelling to Australia and have purchased alcoholic beverages or cosmetics from an airport other than Hamad International Airport, then these will be confiscated at your onward flightβs boarding gate. This procedure is in accordance with Australian regulations.
source : http://dohahamadairport.com/airport-guide/at-the-airport/security-customs
So you're allowed a total of 10 liters of the beverage (5 you, 5 your wife) during transit.