To swear by

to place great confidence in a person or thing; to trust implicitly as an authority.

See also: Swear

References in periodicals archive ?
Therefore [that person who has done these things] has turned back from the true God to swear by those who are not gods.
God, indeed, does not swear by anyone greater, but rather swears by himself--not because it is illicit in itself to swear by the greater person if there could be one greater than him (but there cannot be), but because he does not have anyone greater than himself by whom he could swear.