Remind him of his own scriptures
Him Whom They Have Pierced
Zec 12:10 And I will pour upon the house of David, and upon the inhabitants of Jerusalem, the spirit of grace and of supplications: and they shall look upon me whom they have pierced, and they shall mourn for him, as one mourneth for his only son, and shall be in bitterness for him, as one that is in bitterness for his firstborn.
Zec 12:11 In that day shall there be a great mourning in Jerusalem, as the mourning of Hadadrimmon in the valley of Megiddon.
Zec 12:12 And the land shall mourn, every family apart; the family of the house of David apart, and their wives apart; the family of the house of Nathan apart, and their wives apart;
Zec 12:13 The family of the house of Levi apart, and their wives apart; the family of Shimei apart, and their wives apart;
Zec 12:14 All the families that remain, every family apart, and their wives apart.
There is no regret so deep as the ones that believed a lie