I had done a message regarding this many years ago but by request, I am doing it again, only more in depth. Keriah is the act of tearing one's garment when they are deeply sorrowed, done mostly in mourning. It is shown all through Scripture in the Tanakh and also the B'rit Chadasha. But the execution of the Messiah has a much deeper meaning when you truly know the WHOLE story of Keriah in Scripture.