In his explanation of our customs and tradition, Maharil traces back the custom of Tashlich on Rosh Hashanah to very ancient times. It is performed shortly before sunset on the afternoon of the first day of Rosh Hashanah (unless it falls on Shabbat, in which case Tashlich is done on the second day), by going to the banks of a river, lake, or any stretch of water. There certain prayers are recited, followed by the symbolic shaking of the corners of our garments.

The three last verses of the Book of Micah, which we say at Tashlich, contain the explanation for this custom. We say: “Who is a G‑d like You, pardoning iniquity and forgiving transgression to the residue of his heritage. He retains not His anger for ever, because He delights in kindness. He will again have mercy on us. He will suppress our iniquities; and You will cast (tashlich) our sins into the depths of the sea.”

The Maharil gives us a further explanation of Tashlich. The Midrash tells us that when Abraham and Isaac went to Mount Moriah for the akeidah (binding of Isaac), they had to cross a river, one of the forms that Satan adopted to prevent them from fulfilling G‑d’s command. The floods threatened to swallow them, but Abraham prayed “Save us, O G‑d, for the water has reached our very lives,” and they were saved from the floods. Thus, says the Maharil, no obstacle should keep us back from fulfilling any command of G‑d. He who can show the selfless love of Abraham and his readiness to die for the divine word can be sure that his sins will be “cast into the sea.”

The Tashlich prayer, recited at the banks of a river, lake or sea, where there is fish, has another significance in arousing in us thoughts of repentance. For it reminds us of the insecurity of fishes’ life, and the danger of fish to fall for bait, or be caught in the fisherman’s net. Our life, too, is full of pitfalls and temptations.

We are reminded of the classical parable of Rabbi Akiva, who defied the decree which the Roman Emperor Hadrian tried to impose on the Jews, prohibiting the study of the Torah. Asked why he risked his life by studying and spreading the teachings of the Torah, Rabbi Akiva replied by means of the following parable:

A hungry fox came to the bank of a stream. He saw the fish swimming restlessly in the water. Said the sly fox to the fish: “I see that you are living in mortal fear lest you fall into the fisherman’s net. Come out onto the dry bank, and you will escape the net, and we’ll live happily together, as my ancestors lived with yours.” But the fish scoffed at the cunning fox, and replied: “If in the water, which is our very life, we are in danger, surely our leaving the water would mean certain death to us!”

The Torah is our very life, and we cannot live without it any more than fish can live without water. Could we save ourselves by abandoning our way of life, the way of the Torah?

Such are the reflections that Tashlich arouses in the heart of the worshiper.

Finally, the fish serve as a further reminder of the “ever-watchful eye” of Providence, for fish have no eyelids; their eyes are always open. So, too, nothing can be hidden from G‑d. By the same token, one derives courage and hope through faith in G‑d, for the Guardian of Israel neither sleeps nor slumbers.

In the Middle Ages the custom of Tashlich was used several times to accuse the Jews of casting a spell over the water, or even poisoning it, and the rabbis were, on occasion, obliged to prohibit the observance of Tashlich by their communities in those days, so as not to endanger their lives.