It is interesting to note that while feasting is a fixed and permanent aspect of biblical religion, fasting is occasional and provisional.
We see that very clearly in two passages, one in the Old Testament and one in the New. In the Book of Zechariah, a delegation from Bethel comes to Jerusalem to seek wisdom from Zechariah and the other leaders as to whether or not the several fasts instituted during the exile should be continued now that a remnant has returned and the temple is being rebuilt. The Lord takes the occasion to correct their overly ritualistic and formal approach to spirituality, telling them that justice and mercy were more important aspects of biblical worship (Zechariah 7:9-10). He does finally answer their original question in chapter 8:19, saying: