In Numbers 6, we see the rules for a special type of dedication to the LORD that one can impose upon themselves. They may not eat or drink any grape products (I interpret this to mean alcohol or any sweets, though I suppose that is up for interpretation as honey was fine) and were to let their hair grow long, only cutting it once the vow timing had completed. Should it be cut short by a sudden death in their presence, it was counted a sin (it normally would have only made you unclean) and the vow was reset once they were clean again.
Those who we know took the vow include Samson and Samuel (both from birth), John the Baptist, and Paul the apostle.
We see that Paul partakes in this vow to prove his dedication to the law and to refute those who claimed he thought the law was done away with (Acts 18:18, 21:20-24).
In every case, the vow sets them apart as holy for God’s work.
Links:
202503062244