2,869. The Duration of Nezirus

Hilchos Nezirus 3:1

The duration of an unspecified nazirite term is 30 days. Therefore, if someone declares himself to be a nazir, he must observe this vow for at least 30 days. Even if he said that he would be a nazir for a very long period of time, he need only observe nezirus for 30 days because he didn’t specify a duration.

Hilchos Nezirus 3:2

If someone specified a duration under 30 days, such as if he said that he would be a nazir for one day, for ten days or for 20 days, he must observe nezirus for 30 days. This is because there’s no such thing as nezirus for fewer than 30 days. This principle was transmitted via our oral tradition.