Va'yikra 23:27

[alon]

32. It is a positive commandment to fast on Yom Kippur

Vayikra 23:27 OJB) Also on the tenth day of this seventh month there shall be Yom Kippurim; it shall be a mikra kodesh unto you; and ye shall afflict your nefashot, and offer an offering made by eish unto Hashem.

Leviticus 23:27 (CJB) "The tenth day of this seventh month is Yom-Kippur; you are to have a holy convocation, you are to deny yourselves, and you are to bring an offering made by fire to ADONAI."

It is necessary to fast from evening to evening, and to add on from the non-holy time to the holy period [to begin a bit before the first evening and end the fast a bit after the end of the day]. ...

[alon]

Sept 28, 2014 16:33:46 GMT -8 alon said:

32. It is a positive commandment to fast on Yom Kippur

Leviticus 23:27 (CJB) "The tenth day of this seventh month is Yom-Kippur; you are to have a holy convocation, you are to deny yourselves, and you are to bring an offering made by fire to ADONAI."

It is necessary to fast from evening to evening, and to add on from the non-holy time to the holy period [to begin a bit before the first evening and end the fast a bit after the end of the day]. ...

This is one fence I intend to keep, as this is the holiest day of the year on God's calendar.

To deny, or afflict oneself is a Hebrew idiom for fasting. This is a definite commandment.

As always (at least as I understand it) the higher mitzvoth is to preserve life and health. So if my meds start to tear up my stomach, I will probably eat some toast. But keeping in mind the seriousness of the day I'll keep it to the bare minimum. I plan to drink only water, and have decided to forego my supplements as well.

The 24 hour evening to evening period of the day is covered in Lev 23:32, "It will be for you a Shabbat of complete rest, and you are to deny yourselves; you are to rest on your Shabbat from evening the ninth day of the month until the following evening."