Oath-taking for senior executives has been promoted as a mean to enhance honesty within and towards organizations. Herein we explore whether people who voluntarily sign a solemn truth-telling oath are more committed to sincere behavior when offered the chance to lie. We design an experiment to test how the oath affects truth-telling in two contexts: a neutral context replicating the typical experiment in the literature, and a "loaded" context in which we remind subjects that "a lie is a lie." We consider four payoff configurations, with differential monetary incentives to lie, implemented as within-subjects treatment variables. The results are reinforced by robustness investigations in which each subject made only one lying decision. Our results show that the oath reduces lying, especially in the loaded environment-falsehoods are reduced by fifty percent. The oath, however, have a weaker effect on lying in the neutral environment. The oath did affect decision times in all instances: the average person takes significantly more time deciding whether to lie under oath.