Article 1, Section 4, Clause 2
Joseph Story, Commentaries on the Constitution 2:§§ 827--28 (1833)
§ 827. . . . This clause, for the first time, made its appearance in the revised draft of the constitution near the close of the convention; and was silently adopted, and, so far as can be perceived, without opposition. Annual parliaments had been long a favourite opinion and practice with the people of England; and in America, under the colonial governments, they were justly deemed a great security to public liberty. The present provision could hardly be overlooked by a free people, jealous of their rights; and therefore the constitution fixed a constitutional period, at which congress should assemble in every year, unless some other day was specially prescribed. Thus, the legislative discretion was necessarily bounded; and annual sessions were placed equally beyond the power of faction, and of party, of power, and of corruption. In two of the states a more frequent assemblage of the legislature was known to exist. But it was obvious, that from the nature of their duties, and the distance of their abodes, the members of congress ought not to be brought together at shorter periods, unless upon the most pressing exigencies. A provision, so universally acceptable, requires no vindication, or commentary.
§ 828. Under the British constitution, the king has the sole right to convene, and prorogue, and dissolve parliament. And although it is now usual for parliament to assemble annually, the power of prorogation may be applied at the king's pleasure, so as to prevent any business from being done. And it is usual for the king, when he means, that parliament should assemble to do business, to give notice by proclamation accordingly; otherwise a prorogation is of course on the first day of the session.
The Founders' Constitution
Volume 2, Article 1, Section 4, Clause 2, Document 4
The University of Chicago Press
Story, Joseph. Commentaries on the Constitution of the United States. 3 vols. Boston, 1833.
Easy to print version.