One of the soldiers on duty at Jesus’ cross pierced Jesus’ side to determine whether he was already dead (John 19:34). The text, however, describes a plurality of people piercing him. The reference is to those who in unbelief reject him whom God gave as the Saviour of the world.
7 Behold, he is coming with the clouds, and every eye will see him, even those who pierced him, and all tribes of the earth will wail on account of him. Even so. Amen.