'Gash' in the Bible

“Baldness [as a sign of mourning] will come on Gaza;Ashkelon will be cut off and ruined.O remnant of their valley,How long will you gash yourselves [as a sign of mourning]?

They do not cry out to Me from their heartWhen they wail on their beds [in unbelieving despair];For the sake of grain and new wine they assemble themselves [as if worshiping Baal];They rebel against Me.