βέβαιος, -ον (also -α, -ον; βαίνω),

[in LXX: Est.3:13, Wis.7:23, 3Ma.5:31 7:7, 4Ma.17:4 * ;]

firm, secure: ἄγκυρα, Heb.6:19; metaphorically, sure (esp. "in the sense of legally guaranteed security," Deiss. BS, 109; cf . two foll. words): ἐπαγγελία, Rom.4:16; ἐλπίς, 2Co.1:6; λόγος, Heb.2:2; παρρησία, Heb.3:6; ἀρχή (τ. ὑποστάσεως), Heb.3:14; διαθήκη, Heb.9:17; κλῆσις κ. ἐκλογή, 2Pe.1:10; comp. (-ότερος), προφητικὸς λόγος, 2Pe.1:19.†

(AS)

firm; secure; sure