Travelers, except military personnel, diplomats, members of international organizations, UNIFIL and members of the Lebanese National Social Security Fund or staff cooperative, must have an insurance policy for their whole stay in Lebanon, which will cover in full the costs of medical treatment in case they test positive for coronavirus. Alternatively, the policy can be obtained at the insurance counters upon arrival at Rafik Hariri International Airport-Beirut.
Exceptions apply to:
Children under the age of 2 are exempt from presenting a COVID-19 test.
Travelers with proof of recovery from the virus within the last 90 days prior to boarding. Proof of a recent positive viral test and a letter from your healthcare provider or a public health official stating that you were cleared to travel.
More info at the CDC site
Travelers who did not get tested, are advised to stay home and self-quarantine for 10 days after travel.