Every year at Yom Kippur you'll see arguments about fasting. Many Hebrew Roots types seem to be teaching that we do NOT have to “fast” on Yom Kippur, insisting that fasting became a mere tradition, as the word in Hebrew is not to fast but to afflict or humble oneself; etc.
Well, call me crazy, but here are some scriptures that, for me, tie in that being "afflicted" on Yom Kippur includes fasting, because YHWH definitely afflicted His people when He brought them out of Egypt. For 40 years He "afflicted" them while He continuously taught them obedience to everything He ever commanded, including keeping all the Feasts/Appointed Times – each of which has a special meaning. All other Feast times are for celebrating, Yom Kippur is different, expecting us to "afflict" ourselves :
Deuteronomy 8:2 You are to remember everything of the way in which ADONAI led you these forty years in the desert, humbling and testing you in order to know what was in your heart - whether you would obey his mitzvot or not. 3 He humbled you, allowing you to become hungry, and then fed you with man, which neither you nor your ancestors had ever known, to make you understand that a person does not live on food alone but on everything that comes from the mouth of ADONAI. (CJB)
We also see in Isaiah 58:3. 'Why have we fasted, and You have not seen? Why have we afflicted our beings, and You took no note?’" (ISR)
(Bear in mind the Hebrew has no punctuation, so this is not necessarily two sentences.) In Hebrew its "tzamnu" (fast) and "a'na'inu" (aflict) and "nefeshnu" (soul/being). This seems to clearly tie the idea of "aflict" is to "fast" and that the purpose of fasting is to "afflict the soul".)
Then, there is also Ezra 8:21: "I then proclaimed a fast there, at the river of Ahawa, to humble ourselves before our Elohim," (ISR)
Here "fast" is Hebrew "tzom"; Humble is Hebrew "l'hit'anot", from "anah", meaning afflict. Again, to fast is directly tied to "afflict".
And another! Psalm 35:13: "...I humbled my being with fastings;..." (ISR)
Again: "tzom" is to fast and "anah" is to afflict/humble.
And another: Isaiah 58:5: "Is it a fast that I have chosen, a day for a man to afflict his being?" (ISR)
Again, tzom (fast) is tied to "anah" (afflict). And then there is this thought: One of the human understandings of "soul" (Hebrew: nephesh), is to mean "appetite"...
See Proverbs 23:2-3: "If you have a big appetite [nephesh], put a knife to your throat!" (CJB)
And a second example, Psalm 107:9: "For He has satisfied a longing being [nephesh], And has filled the hungry being [nephesh] with goodness" (ISR)
So to "afflict your souls" (Leviticus 23:27) is literally to fast…