Rashi on Numbers 6:5/רש"י על במדבר ו׳:ה׳

1קדש יהיה means HOLY SHALL IT (not “he”) BE viz., his hair shall be holy. inasmuch as he must let grow freely the hair of his head (lit., so as to let grow the over-growth, פרע, of the hair of his head) (Sifrei Bamidbar 25; Taanit 4a).

2פרע — The word פרע is punctuated (as to its first syllable) with Patach-Katan (Segol) because it is in construct state to שער ראשו and the meaning is: the פרע, the wild growth of שער ראשו — The meaning of the word פרע is over-growth of the hair; similar is (Leviticus 21:10) “He shall not let his hair grow wild (יפרע)”. Growth of the hair of less than thirty days’ duration does not come under the term פרע (Sifrei Bamidbar 25; Sanhedrin 22b).