Charles Ellicott Commentary Numbers 26:4-5

"[Take the sum of the people], from twenty years old and upward; as Jehovah commanded Moses and the children of Israel, that came forth out of the land of Egypt. Reuben, the first-born of Israel; the sons of Reuben: [of] Hanoch, the family of the Hanochites; of Pallu, the family of the Palluites;" — Numbers 26:4-5 (ASV)

Take the sum of the people ... — The verses may be rendered as follows: From twenty years old and upward, as the Lord commanded Moses. And the children of Israel which went forth out of the land of Egypt were these: Reuben, the eldest son of Israel, etc.

The expression “as the Lord commanded Moses” is one of very frequent occurrence in this book. The command was given to Moses, not to the children of Israel generally.

The form of enumeration is concise. The omissions may be supplied as follows:—Reuben—he was the eldest son of Israel. The sons of Reuben were—Hanoch—from him, the family of the Hanochites, etc. (Exodus 6:14; 1 Chronicles 5:3.)