ויצו משה את בני ישראל, Moses commanded the children of Israel, etc. The meaning of the verse is that Moses commanded them at the behest of G'd who had commanded him to address the children of Israel. What was the content of that command? "The tribes of the sons of Joseph are correct in what they are saying." The whole verse is a compliment to the tribes of Ephrayim and Menashe.

זה הדבר, "this is the thing, etc." This expression is explained in Baba Batra 120 as follows: "the daughters of Tzelofchod were permitted free choice of husbands, including husbands who were from different tribes, as it says in our verse לטוב בעיניהם תהיינה לנשים, 'let them be married to whom they think best;'" the question then arises how we can can reconcile this with the words "but let them be married to members of the tribe of their father?" The Talmud answers that these words are not a condition but merely sound advice by the Torah to these girls. Thus far the Talmud. When the Torah said זה הדבר these words were necessary because what preceded them was the Torah's acknowledgment that legally speaking the tribes of Joseph had a sound claim. The Torah therefore had to go on record that the justice of the claim of the tribes of Joseph extended to other daughters inheriting land through their fathers which might become lost to their tribe if such daughters married someone out of their tribe and the Jubilee regulation might alienate such land to the original tribe forever. However, in this single instance of the daughters of Tzelofchod, the general rule did not apply and these daughters were free to be married to men of their choosing even men outside their tribes. The word זה is restrictive and makes an exception of the daughters of Tzelofchod. This is also alluded to in the unnecessary word לאמור in this verse. G'd went out of His way to pay great honour to these girls.

ולא תסב נחלה, "so that an inheritance not move (from one tribe to another), etc. The reason the Torah repeats this both negatively and positively is as I have explained already that it was only well meant advice not legislation. The Torah therefore had to repeat that in all instances other than the daughters of Tzelofchod this was a matter of legislation.

כאשר צוה ה׳ את משה כן עשו, "they did as G'd had commanded Moses." We have to understand why the Torah departed from its usual syntax of first reporting the execution and subsequently the fact that it corresponded to the command, whereas here the Torah reverses the order by writing כן עשו only at the end of the verse.

It appears that the reason is that seeing that in this case the Torah had made an exception and allowed the daughters of Tzelofchod free choice in their marriage partners, the Torah wanted us to know that the daughters of Tzelofchod did not take advantage of the special latitude which G'd had granted to them but abided by the general rule laid down for future generations and married within their tribe. The words כאשר צוה השם refer to what G'd had commanded to daughters in the future who would inherit their father's estate. These girls did not take advantage of the special permission granted to them. Had the Torah used its usual syntax here all we would have learned from the verse would have been that the daughters of Tzelofchod did not contravene G'd's command.