The Perek Said When Putting the Face Down
לדוד, אליך ה' וכו'. The original nusach is “לדוד, אליך ה' נפשי אשא וכו'” (תהילים כ"ה ), arranged according to the alef beis. The Beis Yosef cites it (סי' קל"א ) from the Zohar (above, 19). Its content fits with the reason that one is showing mesirus nefesh for Hashem. This is the accepted nusach of Eidot Mizrach.
Not putting the face down. The minhag in Eidot Mizrach is not to put the face down when saying “לדוד, אליך ה' וכו'” so that it does not resemble the primary form of Tachanun. Instead, they say it sitting with the face up so that it does not resemble the way or intent the Zohar describes. This way, one is not in trouble ח"ו if he does not have the proper kavana (כף החיים סקל"ד ). In contrast, Ashkenazim put their faces down but change the nusach they say (see 24 below).
“רחום וחנון וכו' ה' אל באפך תוכיחני.” There is another nusach taken from Tehillim (פרק ו') – “ה' אל באפך תוכיחנו ,” without the first posuk, which is a posuk of song. Instead, the line “רחום וחנון וכו'” is said at the beginning. This is the minhag of Ashkenazim and many Chassidim (לבוש, מ"ב סי' קל"א סק"ח ). [Those who daven Nusach Ari say לדוד אליך וכו' and רחום וחנון and also put the face down.]
The reason for the minhag not to say לדוד אליך וכו' is to differentiate it from what the Zohar describes, as it is dangerous to say the perek לדוד אליך וכו' without the proper kavanos. Thus, Ashkenazim say the other nusach (מג"א סי' קל"א ססק"ה ). Still, this should also be said with kavana and patience, as it is still related to the concept of putting the face down (שלחן הטהור ס"א ).
