Albert Barnes Commentary Numbers 27:1

"Then drew near the daughters of Zelophehad, the son of Hepher, the son of Gilead, the son of Machir, the son of Manasseh, of the families of Manasseh the son of Joseph; and these are the names of his daughters: Mahlah, Noah, and Hoglah, and Milcah, and Tirzah." — Numbers 27:1 (ASV)

Previously, women in Israel had not enjoyed any distinct right of inheritance. Yet a father, whether or not sons had been born to him, had the power, either before or at his death, to direct part of his estate to a daughter; in such a case, her husband married into her family rather than she into his, and the children were regarded as belonging to the family from which the estate had come. Thus, Machir, Zelophehad's ancestor, although he had a son Gilead, also, it is probable, left an inheritance to his daughter, the wife of Hezron of the tribe of Judah. For this reason, their descendants, among whom was Jair, were counted as belonging to the tribe of Manasseh (Numbers 32:41; 1 Chronicles 2:21 and following).