bebaioō

BDAG divides the eight New Testament occurrences between putting something beyond doubt (Mk 16:20; Rom 15:8; 1 Cor 1:6; Heb 2:3) and making a person firm or established (1 Cor 1:8; 2 Cor 1:21; Col 2:7; Heb 13:9), noting throughout the legal coloring the verb carries in the documentary papyri. LSJ records the same two directions from classical prose onward, with the forensic sense of guaranteeing a title or a sale well attested. Deissmann, and following him Moulton and Milligan, assembled that documentary evidence: βεβαιόω and βεβαίωσις are standard terms of the Greek law of sale, in which the vendor undertakes to warrant the purchaser's title against a third-party claim. Schlier's TDNT article builds on the papyri and argues that the New Testament usage predicates objective validity rather than subjective assurance. Thiselton treats the pairing of 1 Cor 1:6 and 1:8 as deliberate, with ἀνεγκλήτους in v. 8 pushing the second occurrence toward an eschatological guarantee before the tribunal, though he allows the weaker reading of simply keeping believers steady. Harris and Thrall both read 2 Cor 1:21-22 as a cluster of commercial and legal metaphors (βεβαιῶν, σφραγισάμενος, ἀρραβών) rather than as a description of Christian initiation. Attridge takes Heb 2:3 as continuing the forensic force of βέβαιος in 2:2, the message being legally attested by those who heard it, and reads βεβαιοῦσθαι τὴν καρδίαν in 13:9 as inner stability set over against dietary observance. Mk 16:20 falls within the longer ending, absent from Sinaiticus and Vaticanus and judged secondary by Metzger and the UBS committee, so it witnesses to early Christian Greek rather than to Mark's own vocabulary.