Extended Strong's Greek Lexicon (Abbott-Smith based)
confirmation
Usage: βεβαίωσις, -εως, ἡ (βεβαιόω, which see), [in LXX: Lev.25:23 (צְמִיתֻת), Wis.6:19 * ;] confirmation: τ. εὐαγγελίου, Php.1:7; εἰς β., Heb.6:16, a phrase frequently in π. of guarantee in a business transaction (Deiss., BS, 104ff.; Cremer, 140).† (AS)