Extended Strong's Greek Lexicon (Abbott-Smith based)
to testify
Usage: μαρτύρομαι (μάρτυρ), [in LXX: Jdth.7:28, 1Ma.2:56 א)* ;] to summon as witness (M, Th., 25 f.; Hort., 1Pe., 53 f.; Lft., Notes, 29; Ga 203), hence, __(a) to protest, affirm solemnly: before ὅτι, Act.20:26, Gal.5:3; __(b) to adjure, beseech: with dative of person(s), Act.26:22; with accusative and inf., Eph.4:17; before εἰς, 1Th.2:12 (cf. δια-, προ-μαρτύρομαι).† (AS)