Translation:Shulchan Aruch/Orach Chaim/110
110: One leaving for a journey and workers, what they should pray; and the order of prayer of traveling and the house of study.
1 At a time of extreme need, for example if he is on the road or if he was standing to pray in a place that he is worried and fearful that they might interrupt him, or if he could not pray the lengthy prayer with kavvanah, then he says the prayer "Havinenu" after the first three. And after it, he says the last three. And he must say them while standing, and when he will reach his home he need not go back to repeat the prayer. And he does not say the Havinenu prayer during the rainy season, nor in the evening of the departure of Shabbat and a holiday.
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3 One who is going in a place of bands of animals and robbers says the prayer: "Your people's needs are many, etc.". And he does not need the first three, nor the last three; and he says this prayer on the road, as he walks along. And if he can stand, then he stands. And once he will get to a settled area and his presence of mind returns, he goes back and prays the prayer of 18 blessings. (And if he did not go back to pray, it is as if he had forgotten to pray entirely, and it was explained earlier, Chapter 108). (And so it seems from Beit Yosef).
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8 One who enters the house of study should pray: "May it be desirable before You, Adonay, our God and the God of our ancestors, that I should not stumble in a matter of Law, etc.". And on his exiting, he should say: "I give thanks before You, Adonay, my God, that You made my place among those who occupy the house of study, etc.".