Jamieson, Fausset and Brown on Leviticus 25:13

13. ye shall return every man unto his possession, &c.--Inheritances, from whatever cause, and how frequently soever they had been alienated, came back into the hands of the original proprietors. This law of entail, by which the right heir could never be excluded, was a provision of great wisdom for preserving families and tribes perfectly distinct, and their genealogies faithfully recorded, in order that all might have evidence to establish their right to the ancestral property. Hence the tribe and family of Christ were readily discovered at his birth.