I bear witness to you today ... a Hebrew idiom?

The OT expression "I proclaim/announce/bear witness to you today [that]"‏ has been identified by some as a Hebrew idiom. It is often cited as evidence for joining σήμερον with λέγω in Luke 23:43. In this post we will take a look at the Hebrew evidence and the LXX rendering. The idiom takes various forms:

Deut. 30:18  הגדתי לכם היום כי
LXX ἀναγγέλλω σοι σήμερον ὅτι

Deut.  4:26  ‏העידתי בכם היום
LXX διαμαρτύρομαι ὑμῖν σήμερον
 
Deut. 8:19  ‏העדתי בכם היום כי
LXX διαμαρτύρομαι ὑμῖν σήμερον

Deut. 32:46  ‏אנכי מעיד בכם היום
LXX ἐγὼ διαμαρτύρομαι ὑμῖν σήμερον

Jer. 42:19-20 ‏ידע תדעו כי־העידתי בכם היום כי‎‏ 
‎‏ LXX γνόντες γνώσεσθε ὅτι
 
Stretching things a bit some have cited  1Sam 12:5; 1Kgs 1:51 as evidence:

1Sam 12:5 ‏‏עד יהוה בכם ועד משיחו היום
LXX μάρτυς κύριος ἐν ὑμῖν καὶ μάρτυς χριστὸς αὐτοῦ σήμερον

1Kgs 1:51 ‏ישבע־לי כיום המלך שלמה
LXX ὀμοσάτω μοι σήμερον ὁ βασιλεὺς Σαλωμων

The idiom represented in the OT evidence has no formal similarity to the NT idiom found in Luke 23:43[1]: [ἀμὴν] ἀμὴν λέγω ὑμῖν/σοι [ὅτι]. The NT idiom uses the verb λέγω which is a translation equivalent for the Hebrew verb ‏,אמר a word that is never used in the Hebrew idiom. The Hebrew idiom uses the verbs: עוד: to testify, bear witness, c. sf. against one; in favour of LXX διαμαρτύρομαι and ‏‏נגד: to publish, declare, proclaim; LXX ἀναγγέλλω.

Then prefixed [ἀμὴν] ἀμὴν is an essential component in the NT idiom [ἀμὴν] ἀμὴν λέγω ὑμῖν/σοι [ὅτι]. [ἀμὴν] ἀμὴν or an equivalent is never used in the Hebrew idiom we examined in this post. Iver found about 75 samples of the [ἀμὴν] ἀμὴν ... idiom in the NT. This idiom is not found in the OT or LXX.

[1]  In Luke 23:43 the pronoun is fronted ἀμήν σοι λέγω which Iver Larsen explains.
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