attest, certify, manifest, demonstrate, evidence (verb)
provide evidence for; stand as proof of; show by one's behavior, attitude, or external attributes
"His high fever attested to his illness"; "The buildings in Rome manifest a high level of architectural sophistication"; "This decision demonstrates his sense of fairness"
guarantee payment on; of checks
license, licence, certify (verb)
"I am licensed to practice law in this state"
certify, endorse, indorse (verb)
guarantee as meeting a certain standard
"certified grade AAA meat"
declare legally insane
to attest to as the truth or meeting a standard