Jonathan Roth Form 3 Crixus BH3 Acquisition / Jonathan Roth ownership change

                               Power of Attorney

KNOW ALL BY THESE PRESENTS, that the undersigned hereby constitutes and appoints
each and any of Alan I. Annex, Jason T. Simon, Brian J. Gavsie, Terrance R.
Gallogly, and John B. Meyer its true and lawful attorney-in-fact and agent, with
full power of substitution and re-substitution, for the undersigned and in his
or her name, place and stead, in any and all capacities (until revoked in
writing) to:

    1.  sign any and all instruments, certificates and documents appropriate or
        required to be executed on behalf of the undersigned pursuant to
        sections 13 and 16 of the Securities Exchange Act of 1934, as amended
        (the "Exchange Act"), and any and all regulations promulgated thereunder
        (including, without limitation, any joint filing agreement with respect
        thereto), and to file the same, with all exhibits thereto, and any other
        documents in connection therewith, with the Securities and Exchange
        Commission (the "SEC"), and with any other entity when and if such is
        mandated by the Exchange Act or by the bylaws of the Financial Industry
        Regulatory Authority;

    2.  prepare, execute, acknowledge, deliver and file a Form ID (including any
        amendments or authentications thereto) with respect to obtaining EDGAR
        codes, with the SEC;

    3.  seek or obtain, as the representative of the undersigned and on behalf
        of the undersigned, information on transactions in securities, from any
        third party, including brokers, employee benefit plan administrators and
        trustees, and the undersigned hereby authorizes any such person to
        release any such information to such attorneys-in-fact and the
        undersigned approves and ratifies any such release of information; and

    4.  perform any and all other acts which in the discretion of such
        attorneys-in-fact are necessary or desirable for and on behalf of the
        undersigned in connection with the foregoing.

The undersigned acknowledges that:

    1.  this Power of Attorney authorizes, but does not require, such attorneys-
        in-fact to act in their discretion on information provided to such
        attorneys-in-fact without independent verification of such information;

    2.  any documents prepared and/or executed by such attorneys-in-fact on
        behalf of any of the undersigned pursuant to this Power of Attorney will
        be in such form and will contain such information and disclosure as such
        attorney-in-fact, in his or her discretion, deems necessary or
        desirable;

    3.  the attorneys-in-fact do not assume (a) any liability for responsibility
        to comply with the requirements of the Exchange Act for any of the
        undersigned, (b) any liability for any failure to comply with such
        requirements for any of the undersigned, or (c) any obligation or
        liability for profit disgorgement under Section 16(b) of the Exchange
        Act for any of the undersigned; and

    4.  this Power of Attorney does not relieve any of the undersigned from
        responsibility for compliance with the undersigned's obligations under
        the Exchange Act, including without limitation the reporting
        requirements under Sections 13 and 16 of the Exchange Act.

The undersigned hereby gives and grants the foregoing attorneys-in-fact full
power and authority to do and perform all and every act and thing whatsoever
requisite, necessary or appropriate to be done in and about the foregoing
matters as fully to all intents and purposes as the undersigned might or could
do if present, with full power of substitution and revocation, hereby ratifying
all that such attorney-in-fact, or such attorney-in-fact's substitute or
substitutes, of, for and on behalf of the undersigned, shall lawfully do or
cause to be done by virtue of this Power of Attorney.  This Power of Attorney
shall remain in full force and effect until revoked by the undersigned in a
signed writing delivered to such attorneys-in-fact.

                            [Signature page follows]

        IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to
be executed as of this 8th day of March 2021.

                                        Signed:     /s/ Jonathan Roth
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                                        Print Name: Jonathan Roth
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