Numbers 6:12

he shall separate&c. He shall separate anew the whole period of the vow upon which he had originally entered.

a guilt-offering This was the most expensive part of the ritual. Opinions differ as to the exact force attaching to it. But the distinctive feature of the offering in other cases seems to have been that it involved an act of reparation for wrong done (see on Numbers 5:6-8). In the present case it is probably reparation for the delay in the completion of the vow and therefore of the sacrifices which consummated it.