ἐπιβεβαίωσις
From LSJ
καὶ λέγων ὅτι Πεπλήρωται ὁ καιρὸς καὶ ἤγγικεν ἡ βασιλεία τοῦ θεοῦ· μετανοεῖτε καὶ πιστεύετε ἐν τῷ εὐαγγελίῳ → declaring “The time has been accomplished and the kingdom of God is near: start repenting and believing in the gospel!” (Μark 1:15)
English (LSJ)
εως, ἡ,
A further confirmation, Id.Rh.Al.1438b29 (pl.); guarantee, Sammelb. 5240.17 (i A.D.).
Greek (Liddell-Scott)
ἐπιβεβαίωσις: -εως, ἡ, ὡς καὶ νῦν, περαιτέρω βεβαίωσις, Ἀριστ. Ρητ. π. Ἀλ. 33, 1.