I don't know that it's required by the IRS - since they don't actually require bylaws and the organization may not be incorporated anyway. If you are incorporated, the papers you filed to become incorporated are your "organizing instrument", so that's sort of your "birth certificate" as far as the IRS is concerned.
But you'll commonly find a statement like that in Article II: Purposes. (Although sections may be numbered/named differently.)
From the IRS:
Exempt Organization - Bylaws Bylaws are an organization's internal operating rules. Federal tax law does not require specific language in the bylaws of most organizations. State law may require nonprofit corporations to have bylaws, however, and nonprofit organizations generally find it advisable to have internal operating rules.
Here are a couple samples:
Sample 1:
The organization is organized exclusively for the charitable, scientific, literary, or educational purposes within the meaning of Section 501(c)(3) of the Internal Revenue Code or corresponding section of any future federal tax code (hereinafter “Internal Revenue Codeâ€).
Sample 2:
The organization is organized exclusively for charitable, educational, or scientific purposes within the meaning of section 501(C)(3) of the Internal Revenue Code.
Sample 3:
Section 1: Nature of the Corporation. The (name of org) nonprofit corporation formed under the (ref. state statute), which is organized and shall be operated in accordance with the meaning and provisions of section 501(C)(3) of the Internal Revenue Code and the regulations issued thereunder.
Section 2: Primary Purposes: The (name of org) is organized for the purposes set forth in its Articles of Incorporation which are filed within the State of (name of state).
