vouch

To call on (someone) to be a witness to something.

To cite or rely on (an authority, a written work, etc.) in support of one's actions or opinions.

To affirm or warrant the correctness or truth of (something); also, to affirm or warrant (the truth of an assertion or statement).

To bear witness or testify to the nature or qualities (of someone or something).

To back, confirm, or support (someone or something) with credible evidence or proof.

Synonym of vouchsafe (“to condescendingly or graciously give or grant (something)”).

To assert, aver, or declare (something).

In full vouch to warrant or vouch to warranty: to summon (someone) into court to establish a warranty of title to land.

Followed by over: of a vouchee (a person summoned to court to establish a warranty of title): to summon (someone) to court in their place.

To guarantee legal title (to something).