An Old Testament prophecy about the suffering that Christ would undergo on behalf of his elect.
The one upon the cross was the firstborn of all creation.
That his friends and his disciples rejected him reflects the utter and complete humiliation of the Son of God.
Knowing the end in some sense effects the way we deal with the present.
Though this is hymn is typically employed to celebrate a man-made "holy day," it is a wonderful reminder of the unfolding drama of God's revelation that culminated in the advent of Christ.