''Yet the firstborn of man you shall redeem''; the addition of the word ''yet'' serves to differentiate and teach that there is a firstborn who is not redeemed, namely, one that was ravaged. A child with two heads is like one that was ravaged, as he will certainly not live. The Gemara answers: Here it is different, as the Merciful One makes the redemption of the firstborn dependent on his skull, as it is stated: ''You shall take five shekels apiece, by the skull'' (Numbers 3:47), which indicates that there is a case in which a firstborn with more than one skull must be redeemed.

The Gemara returns to its discussion of the baraita: The Master says: ''On your arm''; this is the bicep. The term yad can mean either hand or arm. Therefore, the Gemara asks: From where do we derive this? As the Sages taught: ''On your arm [yadkha]''; this is the upper part of the arm. Do you say that this is the upper part of the arm, or is it only literally on your actual hand, i.e., on the palm of the hand? The Torah says: Don phylacteries on the yad and don phylacteries on the head; just as there, with regard to the head, it means on the upper part of the head, as will be explained, so too here, it means on the upper part of the arm.

Rabbi Eliezer says: This proof is not necessary, as the verse states: ''And it shall be for a sign for you upon your arm'' (Exodus 13:9), which teaches: It shall be a sign for you, but not a sign for others, i.e., one must don the phylacteries of the arm in a place where they are not seen by others. This is the arm, which is usually covered, whereas the hand is usually visible. Rabbi Yitzḥak says: This proof is not necessary, as the verse states: ''Therefore you shall place these words in your heart and in your soul, and you shall bind them'' (Deuteronomy 11:18). This teaches that placing the words, i.e., donning the phylacteries, shall be opposite the heart, on the bicep.

The Gemara relates: Rabbi Ḥiyya and Rav Aḥa, son of Rav Avya, would direct the placement of his phylacteries of the arm and don them opposite his heart. Rav Ashi was sitting before Ameimar, and there was a cut in the sleeve covering Ameimar’s arm, and as a result his phylacteries were visible, as they were not covered by a garment. Rav Ashi said to Ameimar: Doesn’t the Master hold that the phylacteries shall be a sign for you but not a sign for others? Ameimar said to him: This does not mean that phylacteries must be hidden; rather, this was stated in order to teach that they must be donned in a place that is a sign for you, i.e., the bicep, which is generally not seen, but it does not matter if in practice the phylacteries are visible.

With regard to the statement of the baraita that the phylacteries of the head are donned on the upper part of the head, the Gemara asks: From where do we derive this? As the Sages taught: ''Between your eyes'' (Exodus 13:9); this is the upper part of the head. Do you say that this is the upper part of the head, or is it only literally between your eyes? It is stated here: ''Between your eyes,'' and it is stated there: ''You shall not cut yourselves, nor make any baldness between your eyes for the dead'' (Deuteronomy 14:1), Just as there, the phrase ''between your eyes'' is referring to a place on the upper part of the head, as that is a place where one can render himself bald by removing his hair, so too, the place where phylacteries are donned is on the upper part of the head, a place where one can render himself bald.

Rabbi Yehuda says: This proof is not necessary, as the Torah says: Don phylacteries on the arm and don phylacteries on the head. Just as there, with regard to the phylacteries of the arm, it is referring to a place which is fit to become ritually impure with only one type of leprous mark, that of the skin, so too here, with regard to the phylacteries of the head, it is referring to a place which is fit to become ritually impure with only one type of leprous mark, that of a place of hair (see Leviticus 13:29–37).

Rabbi Yehuda continues: This serves to exclude the area which is literally ''between your eyes,'' as there is flesh and the hair of the eyebrows present there, and therefore there is a possibility of leprosy through the growth of a white hair, which is impure according to the halakhot of leprosy of the skin (see Leviticus 13:3), and there is also a possibility of leprosy through the growth of a yellow hair, which is impure according to the halakhot of leprosy of the head or the beard (see Leviticus 13:30).

§ The mishna teaches: With regard to the four ritual fringes on a garment, the absence of each prevents fulfillment of the mitzva with the others, as the four of them constitute one mitzva. Rabbi Yishmael says: The four of them are four discrete mitzvot, and the absence of one does not prevent fulfillment of the rest. The Gemara asks: What is the difference between the opinions of the first tanna and Rabbi Yishmael? Rav Yosef said: The difference between their opinions is with regard to a linen sheet with woolen ritual fringes that has fewer than four ritual fringes. The first tanna maintains that since one is not performing a mitzva, he may not wrap himself in the sheet, due to the prohibition of diverse kinds, i.e., the prohibition against wearing clothing made from a mixture of wool and linen threads. Conversely, Rabbi Yishmael permits one to wrap himself in it, as each ritual fringe is a separate mitzva, and the mitzva of ritual fringes overrides the prohibition against wearing diverse kinds.

Rava bar Ahina said: The difference between their opinions is with regard to a cloak with five corners. It is derived that a cloak of this kind requires ritual fringes (see 43b), but it is unclear whether ritual fringes must be placed on each corner. If each fringe is a discrete mitzva, then the obligation applies to the fifth corner as well, but if it is one mitzva then it applies only to four of the corners of this garment.

Ravina said: The difference between their opinions is with regard to the opinion of Rav Huna, as Rav Huna says: One who goes out unwittingly to the public domain on Shabbat with a four-cornered cloak that does not have all of the requisite ritual fringes attached to its corners is liable to bring a sin offering, because the remaining fringes are not an integral part of the garment. Since they do not enable the wearer to fulfill the mitzva, they are considered a burden, which may not be carried into the public domain on Shabbat. The first tanna agrees with this ruling, whereas Rabbi Yishmael maintains that since each corner with ritual fringes is the fulfillment of a mitzva, one is not liable to bring a sin offering due to carrying on Shabbat for wearing it into the public domain.

Rav Sheisha, son of Rav Idi, said: One who cuts the corner of his garmenthas not done anything of consequence with regard to exempting the garment from the obligation of ritual fringes, as he has rendered it a cloak with five corners, to which the obligation of ritual fringes applies.

Rav Mesharshiyya similarly says: One who ties his garment has not done anything of consequence with regard to exempting the garment from the obligation of ritual fringes. What is the reason? It is considered as though the garment is untied, since the knot can be loosened at any time. And we learned likewise in a mishna (Kelim 26:4): All bound leather jugs, i.e., those whose bottoms are not sewn but tied, are ritually pure, i.e., they are not susceptible to ritual impurity. This is because they are not considered receptacles, as these knots will be untied, except for leather jugs of Arabs, who would tie them with a permanent knot.

Rav Dimi of Neharde’a similarly says: One who sews his garment, i.e., he folded over a long garment and sewed the edges together, has not done anything of consequence with regard to the obligation of ritual fringes, and he must place ritual fringes on the original corners. The reason is that if it is so that he does not need the folded part, which is why he is sewing it, let him cut it and throw it away.

§ The mishna teaches that Rabbi Yishmael says: The four of them are four discrete mitzvot, and the absence of one does not prevent fulfillment of the rest. Rav Yehuda says that Shmuel says: The halakha is in accordance with the opinion of Rabbi Yishmael. The Gemara states: But the halakha is not in accordance with his opinion.

The Gemara relates: Ravina was walking behind Mar bar Rav Ashi on the Shabbat of the Festival when the corner of Mar bar Rav Ashi’s garment on which his ritual fringes were hanging tore, and yet Ravina did not say anything to him. When he arrived at Mar bar Rav Ashi’s house, Ravina said to him: Back there, along the way, the corner tore. Mar bar Rav Ashi said to him: If you would have told me then, I would have thrown off the garment there, as once one of the ritual fringes is torn no mitzva is performed with the rest, and it is prohibited to walk in the public domain on Shabbat wearing such a garment. This is in accordance with the opinion of the first tanna, who disagrees with the ruling of Rabbi Yishmael.

The Gemara raises a difficulty: But didn’t the Master say: Great is human dignity, as it overrides a prohibition in the Torah? This includes the prohibition against carrying on Shabbat in the public domain. That being the case, why would he remove his garment in public?

The Gemara answers: Rav bar Shabba interpreted that statement before Rav Kahana: