as·sure vt as·sured, as·sur·ing1 chiefly Brit: insure2 a: to inform positivelythe seller assured the buyer of his honestyb: to provide a guarantee of
Merriam-Webster’s Dictionary of Law. Merriam-Webster. 1996.
(give confidence to) verb
buoy up, cause to feel certain, cheer, comfort, confirm in conviction, console, convince, deliver from uncertainty, dismiss all doubt, embolden, encourage, en hearten, free from doubt, free from uncertainty, give hope, hearten, inspire, inspire hope, lead to believe, make certain, make confident, offer assurances to, persuade, put at ease, raise expectations, reassure, render certain, restore one's faith, satisfy, set at ease, solace
affirm, agree to indemnify for loss, answer for, asseverate, attest, aver, avouch, avow, certify, confirm, endorse, espouse, give security, guarantee, make a promise, make certain, make sure, pledge, profess, promise, render certain, render safe, secure against loss, solemnly promise, subscribe to, swear, underwrite, verify, vouch for, vow, warrant
avouch (guarantee), bear (adduce), bond (secure a debt), certify (attest), contend (maintain), convince, corroborate, cosign, declare, disarm (set at ease), ensure, guarantee, pledge (promise the performance of), profess (avow), promise (vow), sponsor, swear, underwrite, verify (confirm), vouch
Burton's Legal Thesaurus. William C. Burton. 2006
v.To confirm; to make certain; to make someone else sure of something.
The Essential Law Dictionary. — Sphinx Publishing, An imprint of Sourcebooks, Inc. Amy Hackney Blackwell. 2008.