Blue Techelet Thread

I was in Israel recently and saw some religious men wearing tzitzit strings with a blue thread. I thought the strings were supposed to be white. What was this blue?

The Aish Rabbi Replies:

The Torah prescribes a blue dye called "techelet" to be used as one of the strings on the Tzitzit, and also used for dying priestly garments. (see Exodus 25:4 and Numbers 15:38)

However, Tzitzit are still fit for use even if they lack the blue string.

Techelet was a bluish color, obtained from the fluid of a sea creature called the chilazon (Tosefta Menachot 9:6). It is found on the coast of northern Israel, though there is a disagreement among scholars regarding what the chilazon actually is. Some say it is a snail, others say a squid, and some claim it is another type of mollusk.

At any rate, this particular dye was very precious and because of its value, the Romans (who conquered Israel in 63 BCE) seized control of its usage. This caused the Jewish dyers to go underground. By 639 CE, at the time of the Arab conquest, the secret of techelet was lost all together.

In the 1850s, Rabbi Gershon Henoch Leiner, the Radzyner Rebbe, began to search for the long lost chilazon. What he came up with was a type of squid that fit the Talmud's description. Within a few years, thousands of the rebbe's followers were wearing techelet.

However, in 1913 Rabbi Isaac Herzog (the Chief Rabbi of Ireland and later the Chief Rabbi of Israel) discovered that the techelet dye of the Radzyner Rebbe included iron fillings in the process. Rabbi Herzog ruled that this makes the dye synthetic – and thus unfit for use. Nevertheless, there are still people today who wear the Techelet of the Radzyner Rebbe.

As Rabbi Herzog continued his research, he found that the French zoologist Henri de Lacase-Duthiers had discovered a mollusk called murex trunculus that could create a blue dye. Subsequent research has prompted other Jews to use Rabbi Herzog's techelet.

Today, however, the majority of Jews still do not wear Techelet because we don't have a bona fide tradition coming from the time of the Sages of exactly which animal is used.

Next time you are in Israel, you can stop by the "Temple Institute" located in the Old City of Jerusalem to see examples of wool dyed from the various sea creatures thought to be the Chilazon. To learn more, go to and

There are many esoteric meanings to the techelet thread. The Midrash says, "Whoever observes the mitzvah of tzitzit is considered as if he greeted the Divine Presence, for techelet resembles the sea, and the sea resembles the sky, and the sky resembles God's holy throne." (Sifrei – Shelach) Thus the techelet thread is a method of gaining the highest levels of spirituality.

May the Almighty reveal the secret of the chilazon, speedily in our days!


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