In Parashat Vayigash, Yosef reveals his identity to his brothers and instructs them to return to Canaan and bring Yaakov to Egypt, where Yosef – who had risen to the position of viceroy – will support him and his family during the remainder of the famine years. Just before they leave, Yosef gives one final instruction: "Al tirgezu ba-darekh." This difficult phrase has earned many different interpretations. Rashi begins by citing two Midrashic interpretations from the Gemara (Masekhet Ta'anit 10b). One view explains this instruction to mean that the brothers should not engage in complex halakhic discussion and debate during travel. Another opinion recorded in the Gemara claims that Yosef advises them to travel patiently and ensure to stop over for lodging before nightfall.
Rashi himself suggests that Yosef warned his brothers to refrain from discussing the matter of his sale twenty-two years earlier. The brothers were understandably humiliated upon discovering that they were speaking face-to-face with the brother whom they had tried to eliminate. These feelings of shame could have easily erupted in the form of bitter mutual allegations and finger-pointing as the brothers made their way back to Chevron. Yosef therefore advised them to drop the issue altogether. This instruction would then be seen in light of his earlier emphasis after revealing his identity (45:5) that the brothers had no reason to dwell on their past injustices, since in the end it served to save them and their families from hunger. Here, too, Yosef urges the brothers to leave past events in the past, rather than harboring resentment towards one another over this matter. Ibn Ezra suggests this interpretation, as well.
This verse would then perhaps teach a simple lesson in the area of interpersonal relations: to be able to let go of hurtful events of the past. More often than not, friends, siblings, spouses, and parents-children who have fought in the past and have since rehabilitated their relationship are best advised to simply forget and let go and set their sights on the future, rather than dwelling on the painful experiences of the past.
Several other commentators, including the Ramban, Peirush Ha-Tur, Rashbam and Chzikuni, explain this verse to mean, "Do not be afraid of the trip." The previous verses describe the gifts with which Yosef showered his brothers to bring to Yaakov in Canaan. They had good reason to fear traveling during a period of severe drought with ten donkeys loaded with food and grain. Yosef therefore reassured them that they would not come under the attack of roadside bandits.
A particularly fascinating interpretation is suggested by the Ba'al Ha-Turim. He writes that despite the brothers' newly-discovered royal connection, they should not assume the right to trample on other people's property and damage their crops. Their recent discovery that their brother is the leader of the wealthiest country in the region was a situation of "rags to riches"; after experiencing two years of hunger and hardship, they were suddenly guaranteed complete financial security and royal treatment. Yosef warned them that their sudden transformation must not allow them to neglect those who still suffer the ravages of famine. They must continue to respect the property of the poor, struggling peasants along their travel route, even as they make their way to a future of financial security.