All the days of his vow of separation means as long as the Nazirite has promised to dedicate himself or herself to the LORD. This phrase is the same as the opening phrase of verse 4 (see the comments there), except that it adds the word vow. Good News Translation says “As long as you are under the nazirite vow.”

No razor shall come upon his head: A razor is a sharp tool that is used to shave hair from the skin. At first it was made out of stone, but later out of metal. This clause means Nazirites must never shave the hair on their faces or their heads. Good News Translation renders it well by saying “you must not cut your hair or shave.” Bible en français courant says “He must not cut his hair or beard” (similarly Die Bibel im heutigen Deutsch). We do not recommend this rendering with “beard,” since this instruction concerning Nazirites applies to men and women (see the comments on verse 2). Translators may use the word “shave” (Good News Translation) unless it would imply a beard in the target language. Samson’s words in Jdg 16.17 indicate that the uncut hair is a sign of the Nazirite’s vow and the LORD’s presence with the Nazirite; it does not express dedication to asceticism.

Until the time is completed for which he separates himself to the LORD is very similar in meaning to All the days of his vow of separation. This clause may be rendered “until they have completed their time of dedication to the LORD.”

He shall be holy means Nazirites must be set apart for the LORD’s service, that is, they must be devoted/dedicated to serving the LORD, and therefore they must be treated with respect.

He shall let the locks of hair of his head grow long: Good News Translation says simply “and you shall let your hair grow.” Good News Translation removes the qualifier long, which is clearly implied in the Hebrew verb here.

Quoted with permission from de Regt, Lénart J. and Wendland, Ernst R. A Handbook on Numbers. (UBS Helps for Translators). Miami: UBS, 2016. For this and other handbooks for translators see here .