The Persistence of a Positive Influence
Rashi comments about the encampments of Yehuda, Yissachar, and Zevulan about which it is said, "tov latzadik, tov leshcheno" for they were the neighbors of Moshe who was involved in Torah, and, consequently, they became great in Torah. He goes on to quote phrases that associate these tribes with Torah accomplishments.
My grandfather points out that the verses Rashi cites refer to the tribes later, in the years when they were settled in the land of Israel. Their proximity to Moshe was, obviously, only during the generation of the desert. Yet the influence extended all those generations! He suggests that perhaps the impression set during the formation of the nation was particularly strong so that it would remain effective even in the generations that follow.