The Bible teaches that we are so sinful we are morally unable to please God (Romans 8:7). It also teaches that without faith it is impossible to please God (Hebrews 11:6). Yet salvation is by faith, and we are called again and again in Scripture to believe (Acts 16:31).
How then shall we preach to those who cannot come to Christ, but must come in order to be saved?
John Duncan (1796-1870) was a minister of the Free Church of Scotland and a missionary to the Jews in Hungary. He is often referred to as Rabbi Duncan because of his love for Jewish people. John Macleod wrote that "since the days of the Apostles there is hardly on record such a striking work of grace among the Jews as took place in the days of his labors in Buda-Pesth.”
Here is Duncan’s penetrating answer to our question.
It would not do to tell a man that he may come to Christ, but that he must come. Some, indeed, would have man to do all, though he could do nothing; and others would have him to do nothing, because all was done for him.
As long as I am told that I must come to God, and that I can come, I am left to suppose that some good thing, or some power of good remains in me, and I arrogate to myself that which belongs to Jehovah. The creature is exalted, and God is robbed of His glory.
If, on the other hand, I am told that I cannot come to God, but not also that I must come, I am left to rest contented at a distance from God, I am not responsible for my rebellion, and God Jehovah is not my God.
But if we preach that sinners can't come, and yet must come, then is the honour of God vindicated, and the sinner is shut up. Man must be so shut up that he must come to Christ, and yet know that he cannot. He must come to Christ, or he will look to another, when there is no other to whom he may come; he cannot come, or he will look to himself.
This is the gospel vice, to shut up men to the faith. Some grasp at one limb of the vice and some at the other, leaving the sinner open - but when a man is shut up that he must and cannot, he is shut up to the faith - shut up to the faith, and then would he be shut up in the faith. God is declared to be Jehovah, and the sinner is made willing to be saved by Him, in His own way, as sovereign in His grace. (Rich Gleanings, 392, emphases added)