God would be perfectly just and righteous if he didn't send his Son to save even one sinner. No sinner deserves salvation, neither an offer to salvation, no, not even the common things of providence. I'd be wary of calling God a debtor, for he owes nobody nothing, but we are eternal and infinite debtors. You are blaspheming God, when saying he can't conceive a way, in which he uses and , praise the Lord, repairs his creation the best way possible. You are denying him rights to use his providential power in his more treasured creation - man. Is main omniscient, omnipotent or all-wise, or stronger than the Devil? Then he must be subject to the one who is. And God has special thoughts for that part of his creation.
One day all will cast their crowns of free-will or "good hearts" before the Lord and there will be no questions asked.
11 Thou art worthy, O Lord, to receive glory and honour and power: for thou hast created all things, and for thy pleasure they are and were created.
12 Saying with a loud voice, Worthy is the Lamb that was slain to receive power, and riches, and wisdom, and strength, and honour, and glory, and blessing.
And yet he is not worthy to receive power over our will?
The why here has nothing to do with God changing. God doesn't repent or withhold his promised good, although it may seem so at the surface. David asked the same17 O LORD, why hast thou made us to err from thy ways, and hardened our heart from thy fear? Return for thy servants' sake, the tribes of thine inheritance.
Hath God forgotten to be gracious? hath he in anger shut up his tender mercies? Selah."
But then David realises where his fear comes from:
"10 And I said, This is my infirmity:"
The "Why" is therefore a cry out of weakness, which leads to doubt, human and one that God has favour towards. Now, God is unchangeable and doesn't repent of promises and gifts, which may be hidden from us and the good delayed for a while.
19 God is not a man, that he should lie; neither the son of man, that he should repent: hath he said, and shall he not do it? or hath he spoken, and shall he not make it good?
God does nothing without a purpose, but blesses us with being participants in his Holy and Good purpose. In fact it is this his quality that prevents him from acutally punishing us for our sin accordingly. His mercy is everlasting, because he is unchangeable.
For I am the LORD, I change not; therefore ye sons of Jacob are not consumed.
Once again, the issue at the heart of the issue is the wicked human heart. This intercessory prayer cannot come from an unbelieving heart. If this prayer was from the lips of an apostate or ungodly Israelite, God would have not heard it for a second. The "hardened" ones are the past generations, also, surely the prophet isn't referring to himself, but talks collectively, like in Isaiah 53 and 59 and almost everywhere else. He is laying down the prayer that those who are turned by God will direct at their Lord.
Then shall they call upon me, but I will not answer; they shall seek me early, but they shall not find me:
He that turneth away his ear from hearing the law, even his prayer shall be abomination.
God will only answer a repentant heart, one, which his Spirit has crushed and mashed and infused with grace. Solomon was prophetically aware that one day the nation of Israel will take those steps back or ever beyond their captivity and go into idolatry and, consequent to their failure to maintain the Mosaic covenant, be scattered among the nations. But he also knew that God would not fail his promises, including the one in Deuteronomy, where God promises to give to many of them a new heart and so they would be somewhat restored. This was fulfilled partially in the days of the Babylonian captivity and the Greek invasion and will be fulfilled fully, with the heavenly kingdom, when all the Jews get saved.
Remember, this is not conditioned on anything, this is the new covenant, God performed it, Christ procured it, the Holy Ghost dispenses it and by the merits of Christ we are made partakers of its benefits, chiefly the change of heart.
6 And the LORD thy God will circumcise thine heart, and the heart of thy seed, to love the LORD thy God with all thine heart, and with all thy soul, that thou mayest live.
8 And thou shalt return and obey the voice of the LORD, and do all his commandments which I command thee this day.
1 Kings 848 And so return unto thee with all their heart, and with all their soul, in the land of their enemies, which led them away captive, and pray unto thee toward their land, which thou gavest unto their fathers, the city which thou hast chosen, and the house which I have built for thy name:
49 Then hear thou their prayer and their supplication in heaven thy dwelling place, and maintain their cause,
56 Blessed be the LORD, that hath given rest unto his people Israel, according to all that he promised: there hath not failed one word of all his good promise , which he promised by the hand of Moses his servant.
58 That he may incline our hearts unto him, to walk in all his ways, and to keep his commandments, and his statutes, and his judgments, which he commanded our fathers.
So it is not only a pure and broken heart, but also the whole heart. Shall they call upon the Lord with the whole of their wicked hearts, out of which all kinds of lawlessness and evil outpours (Mark 7; Genesis 6:5)? No, from their new hearts, which God has promised to give them through the circumcision without hands and the operation of the faith of God. Colossians 2:12. This must absolutely precede the heart-felt sincere prayer, which God will hear and is a singular and personal work of God. A fish will sooner jump out of water than a sinner out of his hardened and unrepentant sinful condition. And it all begins in the mind, or, biblically said, the heart.Jeremiah 29: 13 And ye shall seek me, and find me, when ye shall search for me with all your heart.
For as he thinketh in his heart, so is he:
The thoughts of the wicked are an abomination to the LORD: but the words of the pure are pleasant words.
Those, who call upon the name of the Lord with this pure and broken and single heart are bound to be saved, they can do no else and their prayer will be accepted. Lord, to whom shall we go? thou hast the words of eternal life. John 6:68. Whom have I in heaven but thee? and there is none upon earth that I desire beside thee. Ps 73:25. Acts 15:9 And put no difference between us and them, purifying their hearts by faith.
David and Paul knew that the Lord had a purpose for them, before they even knew them:
Ps 71:6 By thee have I been holden up from the womb: thou art he that took me out of my mother's bowels: my praise shall be continually of thee.
Galatians 1:15 But when it pleased God, who separated me from my mother's womb, and called me by his grace,16 To reveal his Son in me, that I might preach him among the heathen; immediately I conferred not with flesh and blood:
Acts 22:14 And he said, The God of our fathers hath chosen thee, that thou shouldest know his will, and see that Just One, and shouldest hear the voice of his mouth.
(This was not only Paul's service appointment, but his salvific experience. He was chosen to be saved and become an apostle at the same time)