On 20 June 1789, the members of the French Third Estate took the Tennis Court Oath in the tennis court which had been built in 1686 for the use of the Palace of Versailles. Wikipedia

Event in the French Revolution. Wikipedia Disambiguation

Pivotal event in the early days of the French Revolution Wikidata

The oath taken on June 20, 1789 in a tennis court in Versailles by the members of the Third Estate not to separate until France has a constitution. OmegaWiki

An oath taken on 20 June 1789 by the members of the French Third Estate, who had begun to call themselves the National Assembly, vowing "not to separate, and to reassemble wherever circumstances require, until the constitution of the kingdom is established"; pivotal in the French Revolution. Wiktionary