דתניא: תפילין, כל זמן שמניחן מברך עליהן, דברי רבי. וחכמים אומרים: אינו מברך אלא שחרית בלבד. אתמר: אביי אמר: הלכתא כרבי, ורבא אמר: הלכתא כרבנן. אמר רב מרי ברה דבת שמואל: חזינא ליה לרבא דלא עביד כשמעתיה, אלא מקדים וקאי ועייל לבית הכסא, ונפיק ומשי ידיה ומנח תפילין ומברך. וכי איצטריך זימנא אחרינא, עייל לבית הכסא, ונפיק ומשי ידיה, ומנח תפילין ומברך. ואנן נמי כרבי עבדינן.
As it is taught: [Regarding] phylacteries (teffilin), while he wears them he blesses them, these are the words of Rabbi. And the sages say: He only utters the morning prayer. It is told: Abbayye says: The law is according to Rabbi and Rava says: The law is according to the rabbis. Said Rav Mari the son of Shmu’el’s daughter: I saw Rava not acting according to this tradition but rather when he goes to the toilet [he removes them and] when he leaves he washes his hands and puts on phylacteries and blesses. And when he needs to go to the toilet again, when he goes out he washes his hands and puts on phylacteries and blesses. And we also act according to Rabbi.
@General observations
This tradition is related in association with the question, does one bless the sukkah and the lulav all seven days or is one day sufficient, and the opinions on the question are divided. The stama by way of analogy raises the issue of phylacteries: Does one bless them only in the morning, when one puts them on, or does one utter blessings on them continually? (And see also above Bavli 2/5. bSukkah 26b). A baraita is presented on this question showing that the issue of phylacteries was also undecided, and Rabbi [Yehudah the Patriarch] holds another opinion than that of the rabbis. Two prominent amoraim, Abbayye and Rava, also disagree as to which of these two opinions the law (halakhah) follows. Rava supports the opinion of the rabbis, but now his student, Mari, son of Shmu’el’s daughter tells a story about his teacher’s hygienic practices, which demonstrate that in life he actually followed the injunction of Rabbi.
@Feminist observations
The tradition transmitted here is placed in the name of a sage designated Rav Mari son of Shmu’el’s daughter. On this sage, designated after his mother, see ILAN, Ta‘anit (FCBT II/9) 247-8.