1) Before beginning the first Bracha of Shemona Esrei, we add the phrase "Hashem Sefasai Tiftach Ufi Yagid Tehilasecha- Hashem, open my lips so that my mouth can relay your praise[with Kavanah]"
This phrase is a "part and parcel" of Shemona Esrei, and as such is not considered a Hefsek (Halachic separation) "Bein G'Eula L'Tefilah"- between The saying of the "Go'al Yisroel " and the beginning of Shemona Esrei.
If one started the first Bracha of Shemona Esrei without first adding "Hashem Sefasai Tiftach", he/she need not repeat Shemona Esrei according to many Poskim. (Biur Halacha Siman 111. Other Poskim argue and maintain that Shemona Esrei must be repeated. See Shu"t Igros Moshe Orach Chaim Vol. 5 Siman 24:8 for a lengthy discussion about this)
2) No other Pesukim or phrases, besides for Hashem Sefasai Tiftach, may be added before Shemona Esrei of Shacharis and Maariv.
Before Mincha and Mussaf, however, other Pesukim may be added before saying Hashem Sefasai Tiftach (as is the established Minhag to indeed add "Ki Shem Hashem Ekra Havu Godel L'Elokeinu" before Maariv and Mussaf).
Even by Maariv and Mussaf, once Hashem Sefasai Tiftach is recited, no other Pesukim may be added, and Shemona Esrei must be started.
Reader's Question:
Regarding your answer [a few days ago] to the question of davening in a car [while driving, where you said that most Poskim prohibit this] , is it permissable to daven while traveling as a passenger in a car?
My Answer
Yes, if you will be unable to daven Shemona Esrei standing at home, in your office, or any other place, you may indeed daven while you are a passenger in a car [or train, or airplane, or bus etc].
If you have a choice to daven only part of davening at home and the rest in a car, it is better to daven Shemona Esrei [while standing] at home first, and only afterwards daven Brachos, Pesukei D'Zimrah etc. in the car.
Our holy sages, the Chazal tell us תנא דבי אליהו כל השונה הלכות בכל יום מובטח לו שהוא בן עולם הבא, שנאמר הליכות עולם לו, אל תקרי הליכות אלא הלכות - one who studies [at least two] Halachos daily is assured a portion in Olam Haba - the world to come. (:מגילה כ"ח )
Important Numbers
