LSJ
                
                
                    confirm, ὑπόληψιν D.L. 8.70; — usu. Med. διαβεβαιόομαι, maintain strongly, affirm, confirm, D. 17.30; οἱ πρεσβύτεροι δ. οὐδέν Arist. Rh. 1389b16; δ. γεγονέναι τι D.S. 13.90, cf. Aristeas 99, D.H. 2.39, BGU 19i17 (ii AD), POxy. 67.10 (iv AD); to be positive, περί τινος Plb. 12.12.6, S.E. P. 1.191; — Pass., Phld. Rh. 1.226S., Sign. 17.
                
                
                    Liddell-Scott-Jones, Greek-English Lexicon (9th ed., 1940)
                
             
                    
                
                    TBESG
                
                
                     δια-βεβαιόομαι, -οῦμαι 
 to affirm confidently: Tit.3:8; before περί, 1Ti.1:7 (Cremer, 140).†
 (AS)
                
                
                    Translators Brief lexicon of Extended Strongs for Greek based on Abbot-Smith, A Manual Greek Lexicon of the New Testament (1922) (=AS), with corrections and adapted by Tyndale Scholars