U.S. Constitution- Legislative Department
Article I. The Congress
Section 1. Legislative Powers
All legislative Powers herein granted shall be vested in a Congress of the United States, which shall consist of a Senate and House of Representatives.
Next: Section 2. The House of Representatives
The Constitution explicitly states in section 1 that it has the power to grant legislative power, and that it does so by having them “vested” in the “Congress of the United States”. The further subdivision mentions the “Senate” first, and the “House of Representatives” second, but they are set forth, more importantly, with the House defined first (in section 2, Article I).