Berakhot 25A

אבל לתפלה עד שיכסה את לבו.

However, for prayer, one may not recite it until he covers his heart, because in prayer he addresses God directly and he must dress accordingly.

ואמר רב הונא: שכח ונכנס בתפילין לבית הכסא ⁠— מניח ידו עליהן עד שיגמור. עד שיגמור סלקא דעתך?! אלא כדאמר רב נחמן בר יצחק: עד שיגמור עמוד ראשון. ולפסוק לאלתר וליקום? משום דרבן שמעון בן גמליאל, דתניא: רבן שמעון בן גמליאל אומר, עמוד החוזר ⁠— מביא את האדם לידי הדרוקן, סילון החוזר ⁠— מביא את האדם לידי ירקון.

And Rav Huna said: One who forgot and entered the latrine while donning tefillin places his hand on them until he finishes. The Talmud wonders: Does it enter your mind that he can do so until he is finished? Rather, as Rav Naḥman bar Yitzḥak said: Until he finishes discharging the first mass of feces, at which point he can step out and remove his tefillin. The Talmud asks: Let him stop immediately when he realizes that he is donning tefillin and stand and step out. The Talmud replies: He cannot do so because of the statement of Rabban Shimon ben Gamliel. As it was taught in a baraita: A mass of feces that is held back without having been discharged causes a person to suffer from dropsy [hidrokan], while a stream of urine that is held back causes a person to suffer from jaundice [yerakon]. Since there is potential danger, the rabbis did not require him to step out.

אתמר: צואה על בשרו, או ידו מונחת בבית הכסא, רב הונא אמר: מותר לקרות קריאת שמע. רב חסדא אמר: אסור לקרות קריאת שמע. אמר רבא: מאי טעמא דרב הונא ⁠— דכתיב: ״כל הנשמה תהלל יה הללויה״.

It was stated that the rabbis disagreed with regard to one who had fecal matter on his skin or whose hand, but not the rest of his body, was placed inside the latrine. Under those circumstances, Rav Huna said: He is permitted to recite Shema. Rav Ḥisda said: He is prohibited from reciting Shema. Rava said: What is the reason for Rav Huna’s opinion? As it is written: “Let every soul [neshama] praise YHWH; Halleluya” (Psalms 150:6), which he interprets as “Let everything that has breath” [neshima]. As long as the mouth with which one recites praise is in a place of purity, the location of the other limbs of his body is irrelevant.