verb
assert, aver, attest, warrant, affirm, verify, confirm, guarantee, asseverate, declare, testify, bear testimony, corroborate, protest, assure, predicate, profess, put forth, maintain, contend, depose, avow, swear, take affidavit, take a Bible oath, go bail on, kiss the Book; see also endorse 2.
Antonyms deny*, repudiate, discard.