This article aims at shedding light on the pragmatic features of speech acts through the constitutionally required oath sworn by newly elected heads of states in democratic countries. These authors focus their study on the oath contained in the article 53 of the 1990 Constitution of the Republic of Benin, that is, to be sworn verbatim under specifically prescribed conditions by every newly elected president of the republic. This is required by law as a prerequisite to the legitimacy as Head of State and the endowment of the power thereof. The paper is based on the speech act theory as originally developed by Austin (1962) and furthered by Searle (1970), whereby every linguistic communication involves linguistic acts. The qualitative approach has been adopted and the exclusive use of commissives highlights the most important goal of this solemn oath which is that of a public commitment by the Head of State to govern as indicated by the people in the Constitution. The study mentioned the decision DCC 96-017 dated on April 5th, 1996 of Benin constitutional court, nullifying the oath sworn on April 4th, 1996, by the then newly elected president Mathieu Kérékou, because his declaration was not completely true to the sacramental and indivisible formula of the constitution, which obliged him to take the oath a second time, on April 6^th, 1996.