They invite their kin to the mountain,
Where they offer sacrifices of success.
For they draw from the riches of the sea
And the hidden hoards of the sand.
ושפני טמוני חול means, covered things that are hidden in the sand — the Tarith (a kind of fish; Rashi in his comment on the Talmudical passage afterwards quoted states that it is the tuna fish), the Chalazon (from which purple dye was obtained) and while glass (all valuable articles of commerce) which come out of the sea and the sand. This was in the territory of Issachar and Zebulun, as it is stated in Treatise Megillah 6a: The Scriptural text (Judges 5:18) is to be explained as follows: “Zebulun was a people that cursed his soul even unto death” because that “Naphtali was on the high places of the field“, i.e., Zebulun complained about his territory, saying, To my brother (Naphtali) you have given fields and vineyards (while to me you have given hilly and mountainous land; to my brother you have given land while to me you have given seas and rivers! God replied. “All your brethren will be in need of you”, as it states, “And the treasures hidden in the sand”, which the Talmud goes on to explain are the marine creatures Rashi mentions above, deriving each of them from the words of the text, For they shall suck … of the concealed treasures of the sea).
The verse should be interpreted as follows: Zebulun said before the Holy One, Blessed be He: Master of the Universe! To my brothers, the tribes whose territory is adjacent to mine, You gave fields and vineyards, whereas to me You gave mountains and hills; to my brothers You gave lands, whereas to me You gave seas and rivers. God said back to him: Nevertheless, all will need you due to the ḥilazon, the small sea creature residing in your territory that is the source of the dye used in the ritual fringes [tzitzit]. As it is stated in Moses’ blessing to Zebulun: “They shall call the people to the mountain: There they shall sacrifice offerings of righteousness; for they shall suck of the abundance of the seas, and of the hidden treasures of the sand” (Deuteronomy 33:19).
§ The Sages taught: This ḥilazon, which is the source of the sky-blue dye used in ritual fringes, has the following characteristics: Its body resembles the sea, its form resembles that of a fish, it emerges once in seventy years, and with its blood one dyes wool sky-blue for ritual fringes. It is scarce, and therefore it is expensive.
We learned in the mishna, among those liable for performing primary categories of labor: One who traps a deer or any other living creature. The Sages taught in a Tosefta: One who traps a ḥilazon and breaks its shell to remove its blood for the dye is liable to bring only one sin-offering. He is not liable for breaking the shell. Rabbi Yehuda says: He is liable to bring two, for performing the prohibited labors of trapping and for threshing, as Rabbi Yehuda would say: The breaking of a ḥilazon is included in the primary category of threshing, as its objective is to extract the matter that he desires from the shell that he does not. The Rabbis said to him: Breaking the shell is not included in the primary category of threshing. Rava said: What is the rationale for the opinion of the Rabbis? They hold: Threshing applies only to produce that grows from the ground. One who extracts other materials from their covering is exempt. The Gemara asks: Even if extracting blood is not considered threshing, let him be liable for taking a life as well. Rabbi Yoḥanan said: This is referring to a case where he broke its shell after it was dead.
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Rava said: Even if you say that he broke it when it was alive, he is exempt. Since he had no intention of killing the ḥilazon, he is considered as one who is acting unawares with regard to taking a life. The Gemara raises a difficulty: Didn’t Abaye and Rava both say that Rabbi Shimon, who rules that an unintentional act is permitted, agrees that in a case of: Cut off its head and will it not die, one is liable? One who performs an action that will inevitably result in a prohibited labor cannot claim that he did not intend for his action to lead to that result. Lack of intention is only a valid claim when the result is merely possible, not inevitable. Since one who extracts blood from a ḥilazon inevitably takes its life, how can Rava claim that his action is unintentional? The Gemara answers: Here it is different, as the longer the ḥilazonlives, the better it is for the trapper, so that its dye will become clear. Dye extracted from a live ḥilazon is a higher quality than that which is extracted from a dead one. Rabbi Shimon agrees that one who performs an action with inevitable consequences is liable only in a case where the consequences are not contrary to his interests. Since he prefers that the ḥilazon remain alive as long as possible, he is not liable for the inevitable consequences.
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The term techelet mentioned throughout the Torah refers to wool dyed light blue - i.e., the color of the sky which appears opposite the sun when there is a clear sky.
The term techelet when used regarding tzitzit refers to a specific dye that remains beautiful without changing. [If the techelet] is not dyed with this dye, it is unfit to be used as tzitzit even though it is sky blue in color. For example, using isatis, black dye, or other dark dyes, is unacceptable for tzitzit.
The wool of a ewe that a goat gave birth to is unacceptable for use as tzitzit.
The Sages taught in a baraita: There is no reliable method of testing sky-blue wool, and therefore it may be purchased only from an expert. There is a method of testing phylacteries to ensure they were written properly, but nevertheless they may be purchased only from an expert. There is a method of testing Torah scrolls and mezuzot, and they may be purchased from anyone.
The Gemara asks: And is there no method for testing sky-blue wool? But didn’t Rav Yitzḥak, son of Rav Yehuda, test it to ensure it was dyed with tekhelet? The Gemara provides a mnemonic for the test, which was carried out with items whose names contain the letters gimmel, shin, or mem. He would bring alum clay [megavya gila], and water of fenugreek [shavlilta], and urine [meimei raglayim]
that was forty days old. He would soak the sky-blue wool in this solution from night until morning. If its color would fade [ipparad ḥazutei], the sky-blue wool was determined to be unfit, as it was not dyed with tekhelet derived from a ḥilazon. If its color would not fade, the sky-blue wool was determined to be fit.