The Treaty of Tripoli was signed in Tripoli on November 4th, 1796. The English text of the treaty was approved by the U.S. Senate on June 7, 1797 and ratified by President John Adams on June 10, 1797. It was recently discovered that the US copy of the Arabic version of the treaty not only lacks the quotation, it lacks Article XI altogether. Instead it seems to contain the text of a letter to the Pasha of Tripoli from the Dey of Algiers.
The person who translated the Arabic to English was Joel Barlow, Consul General at Algiers, a close friend of Thomas Paine--and an opponent of Christianity. It is possible that Barlow made up Article XI, but since there is no Arabic version of that article to be found, it's hard to say.
In 1806 a new Treaty of Tripoli was ratified which no longer contained the quotation.