Siman 49

It is stated in Gittin (60a) that things which are in writing – you are not permitted to say them by heart. And it is derived from a verse, see there. And behold, we pray by heart, and yet in prayer there are many psalms, and Keriat Shema, and Shirat HaYam, and the Akedah, and Korbanot, and how do we say them by heart? However, against this we find in Yoma (70a) that "And on the tenth" in the Book of Numbers the Kohen Gadol would read by heart on Yom Kippur. And in Taanit (28a) regarding the Maamadot, where the men of the Maamad would read the portions of "Bereishit," we say that for Shacharit and Musaf they enter the synagogue and read (from a book), and for Mincha an individual reads it by heart (and the Bartenura wrote because of the burden of the fast). Rabbi Yossi said: And can an individual read words of Torah by heart in public? Rather, they all enter and read it by heart as they read the Shema, see there.

It is clear from the language of Rabbi Yosei that the prohibition is only when an individual reads by heart in public. However, each person for himself—it is permitted. According to this, for us, where each person says it for himself—there is no prohibition here at all. It appears that this is the intent of the Tosafot in Temurah (14b) who wrote: And if you say: How can we say psalms by heart? And one can say that one need only be particular regarding what is written in the Chumash. However, it is difficult: how do we read "Vayosha" and Kriat Shema? And one can say that one need only be particular in a place where he fulfills the obligation of others. Thus far their words. And it is of one intent with that of Taanit, that an individual cannot read by heart in public, meaning: because he fulfills the obligation of others. And as for the fact that the Kohen Gadol would read by heart, one can say that there it was not to fulfill their obligation, for they were not obligated in it at all. And so it is explained in the Zohar Vayakhel (page 206b) that it is only forbidden in public when reading from the Torah.

And in the Yerushalmi in Yoma there they said that the order of the day is permitted to be recited by heart, see there. And the Tosafot Yeshanim in Yoma there also wrote accordingly based on the Yerushalmi, see there. And they further wrote that it is only a mitzvah of the highest standard not to read written matters by heart, but there is no prohibition in the matter. And they further wrote that specifically to fulfill the obligation of others it is prohibited, as the Tosafot wrote in Temurah which we cited. And they further wrote that if so, how does the shaliach tzibbur recite Hallel and fulfill the obligation of others? And they answered: since it is nothing but praise and thanksgiving—we have no concern with it, see there. That is to say: the primary concern is with the Torah, which is the essence of study. And this is also the intent of the Tosafot in Temurah, who wrote that one should only be concerned with what is written in the Chumash, because that is the essence of Torah study. And the Mordechai in Gittin there wrote in the name of Rabbeinu Tam that anything that is common in everyone's mouth—is permitted. And the Tur also wrote this reasoning, and in the name of the Rosh he wrote like the reasoning of the Tosafot, that specifically to fulfill the obligation of others it is prohibited, see there. And our teacher, the Beit Yosef, in the Shulchan Aruch wrote only the reasoning of the Mordechai, see there. And there are those who wrote that a matter of obligation—it is permitted to recite by heart (the Tarei brought in the Beit Yosef). And in the Rambam this is not found at all. And perhaps he holds that just as oral matters are prohibited to be stated in writing, and nevertheless they permitted it because of "it is a time to act for Hashem," so too with written matters that are prohibited by heart—it is also so, because it is impossible for every person to have a book at the time of prayers and songs. And behold, we have written all the words of our teachers in this matter. And according to this, there is no need to be so concerned in this matter, for we have great pillars to rely upon. And I do not know why there are those who were stringent in this (see Magen Avraham and Sha'arei Teshuvah). And a blind person is permitted to read by heart because of "it is a time to act for Hashem" (ibid.). And there is one who wrote that regarding reading the parashah by heart at the time the shaliach tzibbur reads—I am careful, but I do not protest others (ibid. in the name of the Radbaz). And according to the words of our teachers the Tosafot and the Rosh, that only to fulfill the obligation of the public it is prohibited—I do not know of any concern in this, for he is reading for himself.