Again the answer is 'No Transit Visa Required' for Abu Dhabi. People usually get a complimentary hotel stay for that long transit time in the Middle East arranged by travel agent if you request during the time of ticket purchase, and the free hotel is on a first come first serve basis offered by the airline.

If you bought ticket online or your travel agent can't have it booked, you can apply for a transit visa at Abu Dhabi airport & they might grant you one to leave the airport for a hotel - but the hotel won't be complimentary.

Or you can use one of the lounges for a certain number of hours for a nominal fee at the airport.

Good Luck, happy travels!