What is the significance of the term die, die ( מוֹת מוֹת, mûṯ mûṯ) at Genesis 2:17? Die repeated twice

Question

What is the significance of the term die, die (מוֹת מוֹת, mûṯ mûṯ) at Genesis 2:17? Die is repeated twice.

Genesis 2:17 (New International Version):

but you must not eat from the tree of the knowledge of good and evil, for when you eat from it you will certainly die”

Answer 1

As this article explains, repetitions such as this serve as modifiers providing emphasis. The English equivalent would be "very," "every" or, in this case, "surely." Other examples include:

• Genesis 39:10 - yom yom (day day) = every day
• Deut. 16:20 - tzedek tzedek (justice justice) = only justice or true justice
• Deut. 14:22 - shana shana (year year) = each year

See @Robert's answer here for more examples.

Answer 2

While Dan's answer is basically correct, there are Hebrew grammatical structures based on repetition. The Hebrew text at the end of Genesis 2:27 has מֹ֥ות תָּמֽוּת, which the Qal infinitive absolute followed by the Qal imperfect second masculine person singular. This is the standard verbal structure for emphasis.

§ 85. Use of inf. abs. — The inf. abs. is used first, along with the forms of its own verb, to add emphasis. In this case it stands chiefly before its verb, but also after it. Secondly, it is used adverbially to describe the action of a previous verb. And, thirdly, it is used instead of the finite or other inflected forms of the verb. -- Davidson, A. B. (1902). Introductory Hebrew grammar Hebrew syntax (3d ed., p. 117). T&T Clark.

Finally, the infinitive absolute may equally well be represented by a substantive of kindred [the same] stem. In Is 29:14 the substantive intensifying the verb is found along with the infinitive absolute. -- Gesenius, F. W. (1910). Gesenius’ Hebrew grammar (E. Kautzsch & S. A. E. Cowley, Eds.; 2d English ed., pp. 344–345). Clarendon Press.

1. Infinitive absolute of root X + verb of root X (e.g. כָּתוֹב כָּתַב) or verb + infinitive absolute (e.g. כָּתַב כָּתוֹב). This syntactic construction is occasioned by the collocation of an infinitive absolute and a verb of the same stem and stem formation. The stem formations of the infinitive absolute and the finite verb, however, may sometimes differ. Cases in which the infinitive absolute precedes the finite verb (perfect or imperfect) are more common than those in which the infinitive absolute follows the finite verb. Note that when the infinitive absolute is used with a waw consecutive + imperfect, imperative or participle, the infinitive absolute is placed after the particular verb in question. The Hithpael of the infinitive absolute also appears only after the finite form of the verb. This construction usually intensifies the verbal idea. In this way BH speakers/narrators express their conviction of the verity of their statements regarding an action. When a speaker has used this construction, a listener would not be able to claim at a later date that the speakers had not expressed themself clearly enough. -- Van der Merwe, C., Naudé, J., Kroeze, J., Van der Merwe, C., Naudé, J., & Kroeze, J. (1999). A Biblical Hebrew Reference Grammar (electronic ed., p. 158). Sheffield Academic Press.