Numbers 36:4

ואם יהיה היבל may mean AND IF THERE WILL BE THE JUBILEE — From this R. Judah said: The observance of the Jubilee will cease at some time or other (Sifra, Vayikra Dibbura d'Nedavah, Section 13 1 on Leviticus 2:14). ואם יהיה היבל may mean, too: AND WHEN THERE WILL BE THE JUBILEE [THEN WILL THEIR INHERITANCE BE ADDED TO THE INHERITANCE OF THE TRIBE TO WHICH THEY SHALL BELONG] — meaning: This is no sale of land so that it returns to the original owner at the Jubilee, for a heritage never returns. Therefore even when the Jubilee will be, the inheritance will not return to its tribe, and it will follow that it will be added על נחלת המטה אשר תהיינה להם TO THE INHERITANCE OF THE TRIBE TO WHICH THEY SHALL BELONG.

וְאִם־יִהְיֶ֣ה הַיֹּבֵל֮ לִבְנֵ֣י יִשְׂרָאֵל֒ וְנֽוֹסְפָה֙ נַחֲלָתָ֔ן עַ֚ל נַחֲלַ֣ת הַמַּטֶּ֔ה אֲשֶׁ֥ר תִּהְיֶ֖ינָה לָהֶ֑ם וּמִֽנַּחֲלַת֙ מַטֵּ֣ה אֲבֹתֵ֔ינוּ יִגָּרַ֖ע נַחֲלָתָֽן׃

And when the jubilee of the children of Yisra᾽el shall be, then shall their inheritance be added to the inheritance of the tribe unto which they are joined: so shall their inheritance be taken away from the inheritance of the tribe of our fathers.