Tefilas Haderech
Source
1. Torah. We find that Yaakov Avinu said Tefilas Haderech. The posuk (בראשית כ"ח, כ) says, “Yaakov took a neder saying, ‘If Hashem will be with me and guard me on this path I am going on...’”. We also find that when Klal Yisroel traveled in the Midbar, they said the posuk (במדבר י', לה) “ויהי בנסוע הארון ויאמר משה קומה ה' ויפצו איביך וינסו משנאיך מפניך.” The meforshim explain that this was their Tefilas Haderech (דעת זקנים מבעלי תוס', חזקוני).
2. Gemara. The Gemara says (ברכות דף כ"ט ע"), “When you set out to travel, take leave from your Creator and [then] depart...This is Tefilas Haderech.” Chazal also say (שם), “Anyone who sets out to travel must daven Tefilas Haderech. What is Tefilas Haderech? ‘יהי רצון מלפניך וכו' שתוליכנו לשלום ותצעידנו לשלום וכו'.’” This is a mitzvah d’rabanan (ס' ארץ חמד).
Reasons for Tefilas Haderech
3. Protection. One of the reasons Chazal instituted Tefilas Haderech is because travel involves danger, and the Satan accuses in dangerous situations. Thus, one should ask Hashem to protect him from danger.
4. Travel diminishes. Additionally, travel diminishes a person’s money and his name (ירושלמי ברכות פ"ד ה"ד, רש"י תחילת פ' לך לך); Chazal therefore instituted a brachah to prevent these things from becoming diminished (בראשית רבה לך לך פרשה ל"ט).
