Not Prune

Leviticus 25:4 ESV

4 but in the seventh year there shall be a Sabbath of solemn rest for the land, a Sabbath to the Lord. You shall not sow your field or prune your vineyard.

The Hebrew idea translated here as not prune is based on (nâzı̂yr nâzir * naw-zeer'), which has in it's meaning and conveys the idea of setting aside, consecrating. A person known as a Nazarite was one set aside to the Lord with a vow. Not cutting one's hair(no "pruning" or "dressing") is associated with such a vow. 

GWHS

"thou shalt not reap, neither gather [+] the grapes of thy vine undressed:[ nn,pnx [ Noun (61: see 1, 9), Pronominal Suffix (83: see 71) ] H5139 נזר נזיר * nâzı̂yr nâzir * naw-zeer', naw-zeer' * From H5144[H5144 נזר * nâzar * naw-zar' * A primitive root; to hold aloof, that is, (intransitively) abstain (from food and drink, from impurity, and even from divine worship (that is, apostatize)); specifically to set apart (to sacred purposes), that is, devote: - consecrate, separate (-ing, self). [LEX] [Find] ]; separate, that is, consecrated (as prince, a Nazirite); hence (figuratively from the latter) an unpruned vine (like an unshorn Nazirite). (The translation, , is by a false alliteration with Nazareth.): - Nazarite [by a false alliteration with Nazareth], separate (-d), vine undressed. [LEX] NaMzi2r;this masc. noun comes from naMzar (5144). It means a separate one, a dedicated one; a  a prince; the unpruned vine (like an unshorn Nazarite). Nazarites were Hebrew ascetics"