He will take us back in love; He will cover up our iniquities, You will hurl all our sins into the depths of the sea.
One of our main early sources regarding customs among Ashkenazic Jewry is a book by the Maharil, (Rabbi Jacob Moellin) who lived in Germany around 1400. His book is the first documented source we have for the custom of Tashlich on Rosh Hashanah, which is now widespread throughout the Jewish world (though mainly in Ashkenazic communities). He describes walking down to a river after lunch on Rosh Hashanah in order to fulfill the above verse, "to hurl our sins into the depths..." He makes a point of saying that one should not take food along to throw to the fishes for the fun of it, as this might lead to the violation of the restrictions of the holiday. It would seem that the custom was not a new invention by him, and that indeed, he felt constrained to warn people against what probably was common behavior - taking a walk along the riverbank after lunch with the kids, tossing challah crumbs to the fish - perhaps a way to relax between many hours spent in synagogue. Beyond the verse from Micah (which is basically the only "liturgy" for the ceremony), he suggests further justification for the practice: the Torah reading for the second day of Rosh Hashanah is Genesis 22, the binding of Isaac. (It is the reading for the first day in most North American Reform Congregations.) There is a midrash that Satan tried various methods to prevent Abraham from trying to obey God's command; among these was to take the form of a river blocking Abraham's path. Abraham and Isaac continued walking, until the water was up to their necks, at which point God intervened. Hence, a connection between the Rosh Hashanah Torah reading and bodies of water.
The actual origin of Tashlich, and its rationale, are unknown. Some scholars have connected it with the custom of Kaparot on the day before Yom Kippur, when people swing a chicken around their heads while reciting "This is my exchange, this is my atonement..." - which may have its origins in a Roman pagan practice of swinging a pot containing bean seedlings, reciting a similar formula, and then throwing it in the water. And all of these have a certain resemblance to the ritual of the goat for Azazel, the scapegoat (Leviticus 16).
Meanwhile, needless to say, the Maharil's warnings against feeding the fish have been largely in vain. While there are certainly many Jews who see Tashlich as a serious symbolic casting off of sins, scrupulously walking to a body of water and reciting the verse while shaking off invisible crumbs (and there are even rabbis who have objected to this practice, as it seems to imply that such actions can replace true repentance), there are many others who make sure to take plenty of real crumbs along. Sometimes it is fascinating to see the way customs develop a life of their own, even when their origins and/or their meaning have been forgotten. At Shorashim, Tashlich is a family event. People arrive lugging plastic bags full of stale bread. Alas, we are nowhere near a body of water, but there is an ancient rainwater cistern in the center of the community (which no longer collects or holds water). After a brief discussion of the meaning of the ceremony, and a few seasonal songs, everyone crowds around the grate at the mouth of the cistern and dumps their "crumbs." The Maharil would not be pleased. No water. No fish. But something physical and symbolic and not too serious to do on Rosh Hashanah afternoon. Sometimes I wonder what the little kids will remember of this when they grow up, and what they'll pass on to their children - I just hope they don't end up confusing it with Pesach! (Erev Pesach we burn our old bread; on Rosh Hashanah we throw it down a well...).