Lexicon :: Strong's G1263 - diamartyromai

διαμαρτύρομαι; deponent middle; imperfect διεμαρτυρόμην (Acts 2:40 Rec.); 1 aorist διεμαρτυράμην; in the Sept. mostly for הֵעִיד; often in Greek writings from Xenophon down; see a multitude of examples from them in Winers De verb. comp. etc. Part v., p. 20ff; to call gods and men to witness [διά, with the interposition of gods and men; cf. Ellicott (after Winer's) on 1 Timothy 5:21];
1. to testify, i. e. earnestly, religiously to charge: followed by an imperative Acts 2:40; ἐνώπιον τοῦ θεοῦ κ. Χριστοῦ Ἰησοῦ, 2 Timothy 4:1 (2 Kings 17:13; Xenophon, Cyril 7, 1, 17 σὺ μὴ πρότερον ἔμβαλλε τοῖς πολεμίοις, διαμαρτύρομαι, πρίν, etc.); also with ἐνώπιον τοῦ θεοῦ κτλ. followed by ἵνα [cf. Buttmann, 237 (204)], 1 Timothy 5:21 (followed by μή, Exodus 19:21); followed by the infinitive 2 Timothy 2:14 [not Lachmann] (Nehemiah 9:26).
2. to attest, testify to, solemnly affirm: Acts 20:23; 1 Thessalonians 4:6; Hebrews 2:6; followed by ὅτι, Acts 10:42; with the dative of person to give solemn testimony to one, Luke 16:28; with the accusative of the object to confirm a thing by (the interposition of) testimony, to testify, cause it to be believed: τὸν λόγον τοῦ κυρίου, Acts 8:25; τὸ εὐαγγέλιον, Acts 20:24; τὴν βασιλείαν τοῦ θεοῦ, Acts 28:23; for all the apostolic instruction came back finally to testimony respecting things which they themselves had seen or heard, or which had been disclosed to them by divine revelation (Acts 1:21; Acts 5:32; Acts 10:41; Acts 22:18); with the addition of εἰς and an accusative of the place unto which the testimony is borne: τὰ περὶ ἐμοῦ εἰς Ἱερουσ. Acts 23:11; with the addition of a dative of the person to whom the testimony is given: τοῖς Ἰουδαίοις τὸν Χριστὸν Ἰησοῦν, the Messianic dignity of Jesus, Acts 18:5; Ἰουδ. τὴν μετάνοιαν καὶ πίστιν, the necessity of repentance and faith, Acts 20:21 (τῇ Ἱερουσ. τὰς ἀνομίας, into what sins she has fallen, Ezekiel 16:2).

BLB Scripture Index of Thayer's