WCF 3:7. The rest of mankind God was pleased—according to the unsearchable counsel of his own will, whereby he extends or withholds mercy as he pleases—for the glory of his sovereign power over his creatures, to pass by; and to ordain them to dishonor and wrath for their sin, to the praise of his glorious justice.
In the distribution of His electing grace, God passes by unbelievers for their sin and to display his justice. This raises many questions for us. Why didn’t God choose everyone? Isn’t this unfair? There is mystery here that we cannot penetrate. It happens “according to the unsearchable counsel of his own will.” Some receive mercy, some justice and no one injustice. We are ordained to life by sheer mercy, and they were ordained to wrath, for their sin. We ought not think of God’s election or reprobation without understand our radically sinful nature, nor the gracious nature of union with Christ.
WCF 3:8. The doctrine of this high mystery of predestination is to be handled with special prudence and care, so that men, taking heed to the will of God revealed in his Word and yielding obedience to it, may—from the certainty of their effectual calling—be assured of their eternal election. Thus, this doctrine shall provide reason for praise, reverence, and admiration of God; and for humility, diligence, and abundant consolation to all who sincerely obey the gospel.
God has revealed his predestinating grace for the benefit of the people of God. It’s purpose is to bolster their assurance of salvation. This truth is meant to comfort that people of God, not confuse them. And it is also not intended as a tool of evangelism. We bring people to Christ, not Calvin! Believers who wrestle with this doctrine should trust the Word of God and obey it and therefore grow in confidence of their election. The one-sided unconditional grace of election ought to produce praise and adoration of God, and it ought to kill our pride, inspire our growth in grace, and provide true comfort in all events - as we embrace the good news with willing and eager hearts.