Halocho #2200 - May one say Tehillim by heart?

The Torah is divided into two parts: The written-law (Tanach) and the oral-law (Mishna and Gemara).

Even if one knows parts of the written-law by heart, one should be careful not say them without a text.

The exception being those verses that everybody knows by heart, like those תְהִלִּים said often during prayers like אַשְׁרֵי

If possible, one should pray from a Siddur, since Davening includes many verses that not everybody knows by heart. 

Blind people are allowed to say everything by heart.

Source: Kitzur Shulchan Aruch 1:6

- Danny
 Sunday, 15 Tevet 5779

מִזְמוֹרֵי תְהִלִּים וְכֵן שְׁאָר פָּרָשִׁיּוֹת מִתּוֹרָה נְבִיאִים וּכְתוּבִים שֶׁאֵינָם שְׁגוּרִים בְּפִי הַכֹּל, אָסוּר לְאָמְרָם בְּעַל פֶּה

אֲפִלּוּ מִי שֶׁהוּא יוֹדֵעַ לְאָמְרָם בְּעַל פֶּה, יֶשׁ לוֹ לִזָּהֵר שֶׁלֹּא לְאָמְרָם בְּעַל פֶּה

וְסוּמָא מֻתָּר