I am studying the subject of fasting. Did God command the Jews to fast for Yom Kippur? Are there other God-ordained times for fasting?
Fasting isn't commanded by the Bible.
In biblical tradition, fasting isn't commanded. Instead, it was a personal decision, intended to free a person for a period of spiritual concentration. By the second century, however, many Christians followed the practice of twice-weekly fasts. We don't know whether this meant simply not eating during the day (and then eating in the evening) or a full 24 hr fast.