In the Old Covenant, priests had highly symbolic clothing. Among it was a breastplate, which contained four rows of precious stones, each inscribed with the name of one of the twelve tribes of Israel. As the high priest went about his work, he did so with the names of the people on his heart. Jesus, our great high priest, is hours from the cross, and we are on his heart. So he prays. He prayed for his glory. He prayed that we would be kept. And now, he prays for our unity in John 17:20-26. But unity isn't an end in itself, it's unity that points us toward the Son's desire, what he ultimately wants for his beloved people.