2,884. A Nazir Who Doesn't Shave in Purity

Hilchos Nezirus 4:12

If a nazir finishes his nezirus period but he doesn’t shave in purity, he may not shave, drink wine, or become unclean through corpse impurity like before and all the laws of nezirus still apply to him. If he shaves, drinks wine, or renders himself unclean, he is liable to the penalty of lashes.

Hilchos Nezirus 4:13

Let’s say that someone makes a nazirite vow but he thinks that it didn’t take effect so he acts as if he wasn’t obligated by his vow and drinks wine. Later, he consults a Torah scholar, who rules that the vow is effective and that the person must observe nezirus. In such a case, he counts the days from when he took the vow. By rabbinic enactment, he must observe the nazirite prohibitions for the number of days that he acted as if these things were permitted to him.