וְאִם־יִהְיֶ֣ה הַיֹּבֵל֮ לִבְנֵ֣י יִשְׂרָאֵל֒ וְנֽוֹסְפָה֙ נַחֲלָתָ֔ן עַ֚ל נַחֲלַ֣ת הַמַּטֶּ֔ה אֲשֶׁ֥ר תִּהְיֶ֖ינָה לָהֶ֑ם וּמִֽנַּחֲלַת֙ מַטֵּ֣ה אֲבֹתֵ֔ינוּ יִגָּרַ֖ע נַחֲלָתָֽן׃
אַפֿילו אַז יוֹבֿל װעט זײַן בײַ די קינדער פֿון ישׂראל, װעט זײער נחלה בלײַבן צוגעלײגט צו דער נחלה פֿון דעם שבֿט װאָס זײ װעלן צו אים געהערן, און זײער נחלה װעט געמינערט װערן פֿון דער נחלה פֿון אונדזערע פֿאָטערס.
Torah Temimah
It can also be said with a necessary reason that this interpretation, that they were permitted to marry men from all the tribes, is based on the opinion of Rabbi, as stated in Bava Batra 109b. In every portion regarding inheritance, it is stated that it shall be given to them, as it is stated: "And you shall give [the inheritance]" (Numbers 36:4). In the case of a daughter, it is specifically stated: "And you shall cause his inheritance to pass to his daughter" (Numbers 27:8), because you can transfer inheritance from one tribe to another only through a daughter. This is because when she builds her own family and marries, her sons inherit from her, and her husband also inherits from her. For example, Serach, the daughter of Asher, married Chanoch, the son of Reuben, and he died without male children. Serach, his daughter, inherited from him, and when Serach died, her son or her husband, who were from the tribe of Reuben, inherited her portion. Thus, the inheritance of the tribe that belonged to the tribe of Reuben was transferred. Therefore, in the case of the daughters of Tzelafchad, it is also written using the language of transfer: "And you shall cause the inheritance of their father to pass to them" (Numbers 27:7). It is explicitly stated that their inheritance shall be transferred from one tribe to another, according to the meaning and indication of the language of transfer, as explained. Therefore, it is necessary to understand that when it says here "only within the family of their father's tribe shall they marry," it is merely a good advice, as explained, because it is impossible for the inheritance to pass from one tribe to another at all. And the reason why this interpretation relies on the phrase "for their own benefit they may marry" and not on the phrase "and you shall cause to pass," is because it intends to clarify the matter and the order of the verses in its place, and its significance in this portion. This needs further analysis. In the Gemara, it explains that even though it is written "every daughter who possesses an inheritance from the tribe of her father's family shall marry a man from the tribe of her father" (Numbers 36:8), all this applies to other women and not to the daughters of Tzelafchad. Perhaps the reason is that they were important, as explained in the portion of Pinchas, so they were considered under special circumstances. (Bava Batra 120a)
Radak
Yea, a God that is provoked every day: – as though to say, He judges the righteous, and He judges him who provokes God every day, when he repents not of his wickedness. And this is what he means below (by the words) if he turn not – if (אם) being used in the place of כי (when), as: “When (אם) the jubile shall be” (Num. 36:4), where it stands in the place of כי or כאשר (when). And by every day he means “continually.” And how was Saul provoking God? Because he was despising God's work and word, for he knew that David had been anointed as king by the command of God to succeed him, and (yet) he pursued him every day to kill him. You see he was planning every day to bring God's word to naught. And, moreover, David was innocent and had not sinned against him, and he wished to shed innocent blood. And, further, because he had sworn solemnly that he would not slay him. And for all these reasons it was right that He (God) should be spoken of as provoked.
Rashi
ואם תקריב AND IF (according to Rashi, AND “WHEN”) THOU OFFER [A MEAL-OFFERING OF FIRST FRUITS] — אם here has the meaning of כי, “when”, for this (the offering of the מנחת בכורים) is not optional, since Scripture is speaking of the meal-offering of the “Omer” which is obligatory. Similar is אם in the phrase (Numbers 36:4) ואם יהיה היובל which means: “when the jubilee will be”, not: “if the jubilee will be”, since it is bound to come (cf. Sifra, Vayikra Dibbura d'Nedavah, Section 13 2; see also Rashi on Exodus 20:22).