πεπεῖσθαι
From LSJ
Αἰτεῖτε καὶ δοθήσεται ὑμῖν, ζητεῖτε καὶ εὑρήσετε, κρούετε καὶ ἀνοιγήσεται ὑμῖν → Ask, and it shall be given you; seek, and ye shall find; knock, and it shall be opened unto you (Matthew 7:7)
Greek > English (Woodhouse Verbs Reversed)
(see also πείθω): be certain, be confident, be convinced, be positive, be sure