“ויצא יצחק לשוח בשדה לפנות ערב” (כ”ד,ס”ג)
The Gemara in Berachos (34b) says אמר רב כהנא חציף עלי מאן דמצלי בבקתא – I view as arrogant one who prays in an open area such as a valley. Rashi explains that a secluded place is more conducive to fear of Hashem and contrition. Tosafos asks on רב כהנא from this week’s parsha. It says ויצא יצחק לשוח בשדה לפנות ערב, the Gemara in Berachos (26b) explains that Yitzchok was davening mincha, as the word לשוח means תפלה. The passuk says that he was davening in the field which is an open area. This seems to contradict the statement of רב כהנא.
Tosafos offers two answers. The first answer is that Yitzchok was davening on הר המוריה. The meforshim ((ב”ח, ט”ז, מחצית השקל סימן צ’ סעיף ה’ explain that Tosafos means to say that it was מוקף מחיצות surrounded by מחיצות. The כף החיים brings from other meforshim that Tosafos means that since הר המוריה is a holy place, the fear of Hashem is felt even though it is an open area.
According to this we can understand why it is permissible to daven by the כותל המערבי even though it is an open area. The ציץ אליעזר (חלק י”י סימן י”ח ס”ק ב’) explains that the area directly in front of the Kosel is מוקף מחיצות. Even the area further back is also מוקף מחיצות. Reb Chaim Kanievsky shlit”a says that it’s possible the reason is because a חצר is not called an open area.
Tosafos second answer is that רב כהנא is referring to a valley where people and travelers pass through. Tosafos means to say that the reason for this halacha is that the travelers should not interrupt and distract his davening. The בית יוסף asks that this does not seem to be the reason. רב כהנא said חציף עלי it is arrogant to daven this way in an open area, because it shows lack of respect and fear, not because your davening will be interrupted and disturbed? The מגן אברהם explains that Tosafos means to say that if a person davens in such a place he is demonstrating arrogance, as if to say that he is so sure of himself that he won’t get distracted. However the ט”ז understands Tosafos that if he davens in such a place where people pass by then this place itself is not considered a מקום צנוע. According to the ט”ז an open place where no one passes by is still considered a מקום צנוע and one is permitted to daven there.
The ,מחבר (סימן צ’ סעיף ה’) paskens לא יתפלל במקום פרוץ כמו בשדה מפני שכשהוא במקום צניעות חלה עליו אימת מלך ולבו נשבר – one should not daven in an open area like a field, for when one is in a secluded area the fear of Hashem is upon him and he is more broken hearted. According to the בית יוסף this is the first answer of Tosafos.
One should also be careful not to daven in a place where there are people passing by and he will become distracted. As explained above many poskim explain that this is for the same reason why one should not daven in an open area, differently than the understanding of the בית יוסף in Tosafos.
The משנה ברורה says that people who are traveling are permitted to daven in an open area. However if there are trees it is better to daven next to them, because it is an area which is considered to be more צנוע. The אשל אברהם (בוטשאטש) says that standing next to a wall is enough not to be considered an open area. If one has a choice to daven either sitting in his car or standing outside his car, the שו”ת שרגא המאיר says that according to the אשל אברהם he should daven standing outside next to his car, since this is not considered davening in an open area.
Many Rishonim are of the opinion that the prohibition of davening in an open area is only if one is davening by himself, not with a ציבור.
Prepared by R’ Avrohom Yehoshua Ziskind
 Sources:משחת שמן,פסקי תשובות