Rashi on Numbers 3:38/רש"י על במדבר ג׳:ל״ח

1משה ואהרן ובניו [BUT THOSE THAT ENCAMP BEFORE THE DWELLING … SHALL BE] MOSES, AND AARON AND HIS SONS — and adjacent to him was the standard of the camp of Judah, and next to the latter were encamped Issachar and Zebulun — “Well is it with the righteous, well with his neighbour!” Because they (the sons of Judah, Issachar and Zebulun) were the neighbours of Moses who occupied himself with the Torah, they themselves became eminent scholars in the Law, as it is said, (Psalms 60:9) “Judah is my lawgiver”; (I Chronicles 12:32) “and of the children of Issachar which were men that had understanding of the times to know what Israel had to do [the heads of them were two hundred]” — i.e., two hundred heads of the Sanhedrin; and (Judges 5:14) “and out of Zebulun came those that handle the pen of the writer” (Midrash Tanchuma, Bamidbar 12).