From Owen Volume 10:
3. We must exactly distinguish between man’s duty and God’s purpose, there being no connection between them. The purpose and decree of God is not the rule of our duty; neither is the performance of our duty in doing what we are commanded any declaration of what is God’s purpose to do, or his decree that it should be done. Especially is this to be seen and considered in the duty of the ministers of the gospel, in the dispensing of the word, in exhortations, invitations, precepts, and threatenings, committed unto them; all which are perpetual declaratives of our duty, and do manifest the approbation of the thing exhorted and invited to, with the truth of the connection between one thing and another, but not of the counsel and purpose of God, in respect of individual persons, in the ministry of the word. A minister is not to make inquiry after, nor to trouble himself about, those secrets of the eternal mind of God, namely, — whom he purposeth to save, and whom he hath sent Christ to die for in particular. It is enough for them to search his revealed will, and thence take their directions, from whence they have their commissions. Wherefore, there is no sequel between the universal precepts from the word concerning the things, unto God’s purpose in himself concerning persons. They command and invite all to repent and believe; but they know not in particular on whom God will bestow repentance unto salvation, nor in whom he will effect the work of faith with power. And when they make proffers and tenders in the name of God to all, they do not say to all, “It is the purpose and intention of God that ye should believe,” (who gave them any such power?) but, that it is his command, which makes it their duty to do what is required of them; and they do not declare his mind, what himself in particular will do. The external offer is such as from which every man may conclude his own duty; none, God’s purpose, which yet may be known upon performance of his duty. Their objection, then, is vain, who affirm that God hath given Christ for all to whom he offers Christ in the preaching of the gospel; for his offer in the preaching of the gospel is not declarative to any in particular, neither of what God hath done nor of what he will do in reference to him, but of what he ought to do, if he would be approved of God and obtain the good things promised.
Whence it will follow, — First, That God always intends to save some among them to whom he sends the gospel in its power. And the ministers of it being, first,unacquainted with his particular purpose; secondly, bound to seek the good of all and everyone, as much as in them lies; thirdly, to hope and judge well of all, even as it is meet for them, — they may make a proffer of Jesus Christ, with life and salvation in him, notwithstanding that the Lord hath given his Son only to his elect.
Secondly, That this offer is neither vain nor fruitless, being declarative of their duty, and of what is acceptable to God if it be performed as it ought to be, even as it is required. And if any ask, What it is of the mind and will of God that is declared and made known when men are commanded to believe for whom Christ did not die? I answer, first, What they ought to do, if they will do that which is acceptable to God; secondly, The sufficiency of salvation that is in Jesus Christ to all that believe on him; thirdly, The certain, infallible, inviolable connection that is between faith and salvation, so that whosoever performs the one shall surely enjoy the other, for whoever comes to Christ he will in no wise cast out. Of which more afterward.