“Moreover whom He did predestinate …”.
The elect (or the ordained) have been set apart by a decree before the foundation of the world, namely through a decree of the Triune God. For this reason they are called the elect of God. God the Father set them apart. Why them and no others? That will be a mystery forever. God the Father set them apart from everlasting. God the Father laid His hand on them and thereafter He gave them to the Son, for God’s purpose behind the salvation of sinners is the revelation of His divine virtues. “I do not this for your sakes, O house of Israel, but for mine holy name’s sake” (Eze. 36:22).
The Son took them out of the hand of the Father and came under the obligation – after the human nature would have been prepared Him, being made of a woman – to ransom the elect, whom He saw fallen in Adam, from the power of the grave, and to loose them from Satan and condemnation, by His suffering and dying.
And the Holy Spirit, the third Person in the Divine Being, who attended these negotiations, undertook to apply to the elect what had been granted by the Father and would be acquired by the Son, namely by giving Himself to and working in the heart of the elect, thus placing them in possession of the salvation.
By this decree of the Triune God they were set apart from everlasting to everlasting, so that, from the time when man was created, there would be, throughout all the generations, two sorts of people: a people that was chosen by God, and a people that was rejected by God, for the rejection is the reverse of the election. If there were no rejection, we would be unable to speak about election.
In Rom. 9:14 the apostle Paul puts the question: “What shall we say then? Is there unrighteousness with God?”, and his answer (verse 15) is: “God forbid, for He saith to Moses, I will have mercy on whom I will have mercy, and I will have compassion on whom I will have compassion.”
(From: Meditations, 25 January. Sermon on Romans 8:33, 7 April 1932 in Rotterdam)