No man can well doubt the propriety of placing a president of the United States under the most solemn obligations to preserve, protect, and defend the constitution. It is a suitable pledge of his fidelity and responsibility to his country; and creates upon his conscience a deep sense of duty, by an appeal, at once in the presence of God and man, to the most sacred and solemn sanctions which can operate upon the human mind.

Commentaries on the constitution of the United States (ed. 1851)