Menachos 44a: Rav Sheishes said: Anyone who does not put on tefillin transgresses eight positive commandments (the Smag seems to have had in his text the words “every day”).

מנחות מד ע”א: אמר רב ששת: כל שאינו מניח תפילין ־ עובר בשמונה עשה (הסמ”ג במצות עשה ג’ גורס: בכל יום)

ברכות יד ע”א: אמר עולא: כל הקורא קריאת שמע בלא תפילין ־ כאילו מעיד עדות שקר בעצמו.

ר”ה יז ע”א: פושעי ישראל בגופן [שנדונים בגינהם י”ב חודש] מאי ניהו? אמר רב: קרקפתא דלא מנח תפילין.

Rabbi Dovid Tevel, author of Nachalas Dovid (1794-1861), told the following story. A wealthy man passed away, leaving a large estate. Among the possessions he left behind was a priceless pair of tefillin, written by an exceptionally pious sofer, who wrote them in a state of kedusha and purity, with painstaking concern for every detail of the relevant halachos. These tefillin were worth a fortune by themselves.

When the children came to divide up the estate, an argument arose over the tefillin. Each son wanted them and was willing to give up a part of his inheritance in order to receive them. But they could not reach an agreement on how much they were worth. Finally, they decided that rather than fight over the tefillin, they would sell them and divide the proceeds among themselves.

As long as the tefillin were in their possession, however, the brothers agreed to allow a younger brother, who was near bar mitzvah age, to use them. So the boy began putting on the tefillin, and somehow they remained with him.

He was always careful to use only these tefillin. He took them with him wherever he went and guarded them with great care. One winter, he had some business in a number of small villages, so he stayed at an inn on the road and used that as a base for trips to several nearby towns. He intended to return to the inn every night, but one day a sudden snowstorm forced him to spend the night in the home of a gentile with whom he was doing business. When he awakened in the morning, he found out that there was only one Jew in the town. He went straight to this Jew’s home to borrow tefillin and was given a very old and worn pair.

Although he was very apprehensive about putting them on – who could know who had written them – he had no alternative. At the same time, he resolved to return to the inn as soon as he could and put on his own as well. But his business kept them away all that day, and he arrived back at the inn late at night. That was the only time in his whole life that he did not put on his own precious tefillin, and he felt a sense of guilt and remorse about this lapse for the rest of his life.

The years passed and eventually, he went the way of all flesh and was called to the heavenly court to give an accounting of his life. The ledgers were opened, his deeds were examined, and an announcement was made in heaven: “This is a head that did not put on tefillin!” It turned out that the tefillin that everyone had thought to be so exceptionally holy and pure were not even kosher. And this was not a light matter: The Gemara (Rosh Hashanah 17a) says that all those who descend to Gehinom eventually rise again, except for those who sin with their bodies, i.e., those who never put on tefillin.

The Jew was terrified. Fearsome destructive angels grabbed him and were about to cast him into the depths when suddenly an angel appeared and cried out, “Leave him alone! One time he spent the night in a small village and while there, he put on kosher tefillin. He’s not someone who never put on tefillin.” It emerged that the old and worn pair he had put on that day, of which he had been so suspicious at the time, was the only thing standing between him and that terrifying judgment.

Source: The Rosh Yeshiva Remembers, p. 76

[The Smag in Mitzvas Aseh 3 relates that he traveled to Spain in the year 1136 and spoke in front of crowds of Jews to encourage them to adopt the mitzvos of tefillin, mezuzah and tzitzis. Tens of thousands accepted his rebuke and resolved to keep these mitzvos. Among his points were that:

• When Chazal say (Shabbos 49a) that tefillin require a clean body like Elisha Baal Kenafayim, that is only to wear them all the time, but to wear them during tefillah is something anyone can and should do.
• The Gemara says (Menachos 44a) that anyone who does not put on tefillin transgresses eight positive commandments every day, since there are four places in the Torah where tefillin are commanded, and in each one there is a separate commandment for the Shel Rosh and Shel Yad.
• Anyone who recites Shema without tefillin is as if he testified falsely on himself. (Berachos 14a)
• A Jew who did not wear tefillin is called a sinner with his body, and he goes to Gehinom for 12 months and then becomes ashes under the feet of the tzaddikim (Rosh Hashanah 17a). Rabbeinu Tam explains that this means only when he deliberately and rebelliously ignored the mitzvah. The Rif explains that it means only if he never put on tefillin in his life. But, says the Smag, neither Rabbeinu Tam nor the Rif can prove that his explanation is correct. Therefore, one should be stringent.

Based on the above, it seems that the Jews in the Smag’s time had been relying on the Rif and putting on tefilliin only once in a lifetime. The Smag came and convinced them that they should put them on every day.

The Smag is the reason why the protagonist of our story was so upset that he had missed a day of wearing his father’s special tefillin. In the end, the heavenly court ruled like the Rif that once in a lifetime was enough to spare him from Gehinom. But the Smag may still have been correct that the mitzvas aseh is to put them on at least once a day. Reb Dovid Tevil may not have known what happened in the heavenly court, but perhaps he just meant to say that after the man died, they checked the precious tefillin and found them posul. He added the part about the heavenly court because he, Reb Dovid, paskened like the Rif.]

Menachos 21a: One who eats cooked blood does not transgress [the Torah prohibition].

מנחות כא ע”א: אמר זעירי א״ר חנינא: דם שבישלו אינו עובר עליו.

A woman came to the Taz and asked, “I cooked meat, but forgot whether I salted it beforehand.” The Taz permitted it because of ספק דרבנן לקולא – in a doubtful situation on an enactment of the Sages, we rule leniently. We salt meat to remove its blood, but even if we did not remove the blood, once the meat is cooked, cooked blood is forbidden only Rabbinically. Therefore, salting is only a Rabbinic question. Although the rule is that even a doubtful situation of a Rabbinic law, where there is a חזקה – a status quo situation where it is forbidden – we rule strictly, in this case the fact that the meat originally had blood is not considered a חזקה.

The Taz proves this from a case in Shulchan Aruch: meat was known to be soaked and salted, and then a non-Jewish employee cooked it, saying that he soaked it a second time. We rely on his words if he is מסיח לפי תומו – he is speaking casually, not aware that we are relying on him. Now, “speaking casually” is only relied upon when the prohibition is Rabbinic and there is no חזקה. So it must be the fact that the meat originally had blood is not considered a חזקה.

Why not? The Chavos Daas explains that the meat is one thing and its blood is another. The meat itself was never forbidden, only it had blood mixed into it. By salting, we are separating the two, but we are not permitting anything that was previously forbidden.  

The Shach (Nekudos Hakesef) disagrees and argues that in the case of the non-Jew, if there were no חזקה we would permit the meat even without the non-Jew’s casual testimony because every Rabbinic doubt is permitted (ספק דרבנן לקולא). From the fact that we do require his מסיח לפי תומו, we see that blood in the meat is called איתחזק איסורא. And why then is he believed? The Shach (Sifsei Kohein) already explains that non-Jews care about cleanliness and it is likely that he washed the meat anyway. Therefore, here in the case of the woman who is unsure whether she salted the meat, we follow the חזקה  and the meat is forbidden.

The Taz adds that she probably followed habit and salted the meat. To this, the Shach responds that since salting is a big job, the fact that she doesn’t remember it probably means she didn’t do it

[Seemingly there is a big question on this Taz. If blood in meat is not איתחזק איסורא, then treife taste absorbed in a pot is also not איזחזק איסורא for the same reason: the pot is one thing and the treife taste is another, and we are only separating the two. But the whole source for the rule that מסיח לפי תומו is not relied upon by an איסורא דרבנן דאיתחזק איסורא is the end of Siman 137, which says that aנכרי מסיח לפי תומו  is not believed to say that a pot was kashered!

This same question can be asked in Siman 102 in the laws of דבר שיש לו מתירין. The Rema (s’if 4) states that meat with blood in it is not דבר שיש לו מתירין because the meat itself doesn’t need to become permitted; the blood merely has to be extracted. But in s’if 3 all agree that treif utensils would be דבר שיש לו מתירין, if not for the fact that it would be expensive to kasher them.]

Source: Taz, Yoreh Deah 69:24