Hath not the potter power over the clay — And much more hath not God power over his creatures, to appoint one vessel, namely, the believer, to honour, and another, the unbeliever, to dishonour?
If we survey the right which God has over us, in a more general way, with regard to his intelligent creatures, God may be considered in two different views, as Creator, Proprietor, and Lord of all; or, as their moral Governor, and Judge.
God, as sovereign Lord and Proprietor of all, dispenses his gifts or favours to his creatures with perfect wisdom, but by no rules or methods of proceeding that we are acquainted with. The time when we shall exist, the country where we shall live, our parents, our constitution of body and turn of mind; these, and numberless other circumstances, are doubtless ordered with perfect wisdom, but by rules that lie quite out of our sight. But God's methods of dealing with us, as our Governor and Judge, are dearly revealed and perfectly known; namely, that he will finally reward every man according to his works: "He that believeth shalt be saved, and he that believeth not shall be damned."
Therefore, though "He hath mercy on whom he willeth, and whom he willeth he hardeneth," that is, suffers to be hardened in consequence of their obstinate wickedness; yet his is not the will of an arbitrary, capricious, or tyrannical being. He wills nothing but what is infinitely wise and good; and therefore his will is a most proper rule of judgment. He will show mercy, as he hath assured us, to none but true believers, nor harden any but such as obstinately refuse his mercy. Jeremiah 18:6-7