Tractate Berakhot of the Talmud of Eret—-Israel: 0022

1:
The first mishnah of this chapter discussed the time when Shema should be recited in the evening. The second mishnah, to which we now turn our attention, discusses the time when Shema should be recited in the morning.

2:
The first clause of our mishnah states that the earliest time for reciting Shema in the morning is when there is sufficient natural light to distinguish between blue and white. (Let us note that clearly this time will be some time after dawn and before sunrise.) The language of the mishnah suggests a distinguishing between colours: anything blue from anything white — say a cloud against the azure sky. However, the Gemara points out that this reading may be incorrect and a more correct version of our mishnah would be "between its blue and its white". This refers to the tzitzit on a tallit (prayer shawl).

3:
The Torah legislates that the tzitzit on the four corners of the tallit must consist of white threads and one blue thread:

In the Gemara [Menaḥot 42b[ we learn that the blue fringe of the tzitzit was made from a dye that was extracted from a sea snail:

Over the centuries the identity of this sea snail was lost and we had to make do with just the white threads. However, Rabbi Isaac Herzog, who was the Chief Rabbi of Israel [1937-1959], identified the snail. Here is an extract from Wikipedia:

The Murex trunculus, a sea snail (also known as the Hexaplex trunculus), is popularly advanced as the source of the coveted dye. Rabbi Herzog wrote his doctoral thesis in 1913 on the subject and named the Murex snail as the most likely candidate for the dye's source. Though the Murex fulfilled many of the Talmudic criteria, Rabbi Herzog's inability to consistently obtain blue dye (sometimes the dye was purple) from the snail precluded him from proclaiming that the dye source had been found. In the 1980's, Otto Elsner, a chemist from the Shenkar College of Fibers in Israel discovered that if a solution of the dye was exposed to sunlight, blue instead of purple was consistently produced. In 1988 Rabbi Eliyahu Tavger dyed tekhelet [blue] from Murex trunculus for the mitzvah of tzitzit for the first time in over 1300 Years. Based on his groundbreaking work, four years later, the Ptil Tekhelet Organization was founded to educate about the lost making of tekhelet blue and to make authentic tekhelet blue available for all who desire to perform the mitzvah.

My own tallit has such a blue thread on each of its four corners.

4:
So, the Gemara says that when there is sufficient natural light to distinguish between the blue thread of the tzitzit from the white ones the Shema may be recited. After the verses quoted above the Torah continues:

The Hebrew word oto in the phrase "look at it" is susceptible of several interpretations. The sages say, quite reasonably, that here oto means "it" and refers to the thread of blue. So, "look at it" — distinguish it from the white threads next to it — in order to tell whether the time has arrived to recite Shema.

5:
Rabbi Eli'ezer requires somewhat more light than the rest of the sages. He agrees that in the command of the Torah the word oto refers to the tzitzit, but holds that one should be able to distinguish between the blue and any other similar colour — green, for example.

6:
Rabbi Me'ir offers a homily to explain the purpose of the blue thread in the tzitzit: the blue recalls the sea, the sea recalls … the sky, the sky recalls the divine throne. Thus we fulfill the command to "recall all God's commandments and observe them". Rabbi Me'ir interprets the word oto as meaning "Him", God.

7:
But "him" can also refer to a person. So there are others who say that there must be sufficient natural light to recognize someone else at a distance of two metres (6 feet). But who is this person? Is it someone we know? Is it a stranger? This dilemma is resolved by suggesting that there must be sufficient natural light to recognize someone who is a casual acquaintance — such as a guest in a hotel. Other suggestions are also offered: telling a dog from a wolf or one kind of ass from another.

8:
However, all these interpretations of the mishnah (and the Biblical text) are concerned with the earliest time that Shema may be recited in the morning. But is the earliest time the optimal time? It seems not! The Gemara says that the best time to recite Shema in the morning is when one will finish the benediction which comes after Shema at exactly sunrise so that one will commence to recite the Amidah immediately after sunrise. (We have already discussed this at some length: see 0018.)

9:
However, even this "late" hour should not be seen as the latest hour possible for reciting Shema. Rabbi Yehudah says that once, when he was still a student, he was walking after Rabbi El'azar ben-Azaryah who was deep in conversation with Rabbi Akiva about some mitzvah or other: in other words, Torah study, Talmud Torah. When the time came to recite Shema he was surprised that they did not cut off their conversation in order to fulfill the mitzvah. He recited Shema. Later on, when the sun was already high above the mountain tops, the two sages concluded their conversation and started to recite Shema! We shall return to this question later in this mishnah.