From the summary of Constitutional Authority Statements and the Powers of Congress: An Overview (R44729, Mar. 11, 2019):
On January 5, 2011, the House of Representatives adopted an amendment to House Rule XII to require that Members state the constitutional basis for Congress’s power to enact the proposed legislation when introducing a bill or joint resolution. (The amendment does not pertain to concurrent or simple resolutions). This Constitutional Authority Statement (CAS) rule, found at House Rule XII, clause 7(c), was subsequently adopted by every subsequent Congress.
A CAS is fundamentally a congressional interpretation of the Constitution, in that House Rule XII requires each Member introducing a piece of legislation to attach a statement that cites the power(s) that allows Congress to enact the legislation.