Ezekiel 44:20

Neither shall they shave their heads
As the priests and worshippers of Isis and Serapis did, as Jerom on the text observes; and as the Romish priests now do, from whom the Lord's faithful ministers must be distinguished: nor suffer their locks to grow long;
as the Nazarites, that a distinction might be preserved between those who were and were not such; or rather, after the manner of women, their locks hanging down, and flowing about their shoulders, as a token of levity, wantonness, effeminacy, pride, and vanity; see ( 1 Corinthians 11:14 1 Corinthians 11:15 ) : they shall only poll their heads;
observe a medium between both; neither shave their heads close, nor let their hair grow long, but keep it in an even moderate length; for which reason godly men of the last age among us were called "round heads".