Sclater:

And hated Esau] That is, Reprobated Esau: Now that there is Reprobation, appears, because there is Election. 2. God has not Mercy on all. 3. There are Vessels of wrath prepared to destruction, Rom. 9:22, and Jude 4, ordained to this judgement. 4. Effects, denial of means to many for Salvation.

If any ask what it is? Reprobation is an Act of God whereby he determines, not to have mercy on some, but to leave them to destruction, for the glory of his justice. For the moving cause of Election that that may be known, we are to conceive the Acts of Reprobation to be two. 1. A decree not to have mercy; this Absolute, and has no other cause, but the Will of God; And let none say, this is injury, for God is bound to none. Rom. 11:33, therefore, Saint Paul refers to all God’s Will, and admits the depth of this secret, which had been vain, if the cause thereof be foresight of sin and disobedience. 2. The second Act, is ordination unto punishment, and Damnation; this has some respect unto sin, being an Act of Justice, in respect to Execution: And therefore, though it be true that God refuses to show mercy only because he will; yet he ordains no man to damnation, but for his sin; Judas damned for his sin; Comparative, why this not that, no other cause, but God’s Will.

William Sclater, A Brief and Plain Commentary with Notes: Not More Useful, than Seasonable, upon the whole Prophecie of Malachy (London: Printed by J.L. for Christopher Meredith at the sign of the Crane in Pauls Church-yard, 1650), 15.

[Notes: That last sentence may be confusing. What he is saying is that if we ask the question, “Why is this man condemned?” Scalter would say, “That man is condemned solely on account of his sin.” If we ask the second question: “Why is this man elected, but not that man?” Sclater would answer, “This man is elected, but not that man, because of the absolute will of God alone.” For the Reformed, in the first act of reprobation, namely Preterition, man is rejected solely because of the free will of God. In the second act, namely Predamnation, however, man is condemned on account of his sin only. C.f. Heppe and Leigh.]