The phrase “the day of the LORD” (יוֹם־יְהוָה֙) in OT literature is a phrase with deep meaning and significance. This phrase is often found in prophetic literature in the context of a significant period of time in the future. It’s a big topic!
One resource that discusses this phrase is the New International Dictionary of New Testament Theology and Exegesis (NIDNTT). Though it is a New Testament Greek dictionary, one strength of the NIDNTT is that it also talks about the OT background of many NT words and phrases. For example, under the heading of “day” (ἡμέρα), it includes a discussion of “day” in Jewish literature, including the Septuagint and Hebrew Bible. It’s a pretty detailed discussion! Here’s a paragraph from that section I found helpful. It is a little “thick,” but it’s worth reading:
In addition, the OT contains adverbial expressions of time such as בַּיּוֹם הַהוּא (“on that day,” used of the past c. 90× and of the future c. 110×) and הַיּוֹם 2 (“today,” used of the present, c. 215×). The central part of [Simon] DeVries’s monograph [called “Yesterday, Today, and Tomorrow”] consists of a detailed examination and classification of these various passages, taking into consideration their literary form. Of theological significance is his conclusion that the function of the references to Yahweh’s day, whether in the past or the future, is to illuminate the present “today.”
“Historiography provides the model for parenesis, employing the image of revelatory event in the past to illuminate the revelatory significance of the present. Eschatology is, then, an analogical projection of the past and the present into the future, positing Yahweh’s coming action on his action already experienced” (DeVries, Yesterday, Today and Tomorrow, 341). Any day may become Yahweh’s day, but only those days actively become his day when he manifests himself in judgment and salvation (cf. Ps 95:7 [94:7]; Jer 28:9 [45:9]; Ezek 33:33; Mal 3:2, 4, 17–18).
Again, there’s a lot to digest in those two paragraphs. One great sentence in the previous quote that sticks out to me is the one I’ll end with – so you can think more about it as well!
“Eschatology is, then, an analogical projection of the past and the present into the future, positing Yahweh’s coming action on his action already experienced”
The slightly edited quotes from above are taken from the NIDNTTE’s entry on the word group “day”.
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