Or HaChaim on Numbers 8:4/אור החיים על במדבר ח׳:ד׳

1 וזה מעשה המנורה, And this is how the candlestick was made; The reason this verse is repeated here a third time after we have read it in Parshat Terumah as well as in Parshat Vayakhel, can be explained both according to those who hold that the lamps were detachable as well as according to the scholars who hold that the lamps were an integral part of the cast candlestick. We have explained that the word בהעלותך as distinct from בהדליקך meant that the candlestick had to be taken apart in order for the lamps to be prepared. This in turn might have led one to believe that the remainder of the candlestick did not have to be cast from one piece seeing the lamps were included in the description of the "candlestick." We could therefore have applied an exegetical method of דבר שהיה בכלל ויצא (compare Baraitha of Rabbi Yishmael, introduction to Sifra on Leviticus) according to which other parts of the candlestick would also qualify even if they were detachable. The fact that the verse specifically mentions the word מקשה, cast, would only have referred to the initial construction of the candlestick. Once it had been made according to G'd's instructions it would have been permissible to detach sections in a manner that allowed them to be re-assembled. The Torah had to repeat the manner in which the מנורה was to be made to ensure that we would not arrive at such a faulty conclusion. The repetition means that the candlestick was to remain exactly as it had been cast originally. The scholars who hold that the candlestick was cast including the lamps can accept this interpretation also.