Numbers 3:1 - Albert Barnes' Notes on the Bible

The “generations” (see Genesis 2:4) now given, though entitled those of Aaron and Moses (Aaron standing first as the older brother), are those of Aaron only. The personal dignity of Moses, though it gave him rank as at the head of his tribe, was not hereditary. He had, and desired to have Numbers 14:12; Exodus 32:10, no successor in his office but the distant prophet like unto himself Deuteronomy 18:18. Aaron was the ancestor of a regular succession of priests.