Today as I read from Isaiah 6, it struck me how Isaiah's salvation and call to ministry are all of grace. Of course Scripture as a whole shows us that our salvation is of the Lord and that we have absolutely nothing to do with earning it or being gifted it. It is unconditionally granted by God at His pleasure according to His will for His glory.
But it seems to me Isaiah 6 gives us a beautiful illustration of how God calls us to salvation and then to walk in light of that salvation by calling others to faith and repentance, even if it's a heart-breaking task that seems to us to yield little fruit.
Let's begin with verses 1-7:
Isaiah's experience with the Lord is ordained from all eternity, but happens in time. It occurs in the year King Uzziah died. We see Isaiah does nothing to seek God's presence or favor, but that the initiative is God's. God suddenly draws Isaiah into a vision of Himself in His glory.
6:1 In the year that King Uzziah died I saw the Lord sitting upon a throne, high and lifted up; and the train  of his robe filled the temple. 2 Above him stood the seraphim. Each had six wings: with two he covered his face, and with two he covered his feet, and with two he flew. 3 And one called to another and said:
“Holy, holy, holy is the Lord of hosts;
the whole earth is full of his glory!” 
4 And the foundations of the thresholds shook at the voice of him who called, and the house was filled with smoke. 5 And I said: “Woe is me! For I am lost; for I am a man of unclean lips, and I dwell in the midst of a people of unclean lips; for my eyes have seen the King, the Lord of hosts!”
Yet God doesn't just wow Isaiah with His glory, he lets him hear a sermon of sorts, which is actually a song of praise being sung by the seraphim, who are ascribing holiness to God and declaring that the "whole earth is filled with His glory." Interestingly enough, Isaiah records that the seraphim are not addressing Isaiah nor are they directly addressing God. They are "addressing one another" and singing the praises of God's holiness and glory. Even before the throne of God they are preaching and declaring to one another God's infinite worth and pure holiness, and God chooses to show this ongoing worship to Isaiah so that he might not just see and believe but hear and repent.
Undone by the weight of God's holiness and glory and the depths of his depravity and unholiness, Isaiah declares woe upon himself, confessing not just his generic sinfulness and uncleanness, but a particular besetting sin (unclean lips). He contrasts this with God's perfection and declares he is lost, that he is a goner. He recognizes no works or deeds on his part can justify or appease or propitiate the wrath of the holy Lord of hosts.
So what happens next? Even before he can plead for mercy, a seraph "flew" to him with cleansing fire from the altar, touching Isaiah's mouth with the burning coal and declaring absolution. Isaiah's guilt is taken away and his sin atoned for.
Remember, this happens immediately after Isaiah declares his utter inability to save himself. This happens not because Isaiah convinced God to save him but because God granted salvation of His own initiative to Isaiah and because the Lord is slow to anger but abounding in steadfast love, quick and eager to forgive the repentant sinner.
The grace to save Isaiah, to remove his guilt and atone his sins was all from God, wholly unearned or merited. It came immediately after Isaiah was brought to an awareness of his brokenness and sinfulness in light of God's holiness, and that awareness of God's holiness was made by divine revelation and by preaching the glory and holiness of God by the seraphim.
So Isaiah has seen the Lord's glory and lived to talk about it. What happens next? Let's look at verses 8-13:
Isaiah is saved, and as a fruit of his salvation and repentance he desires to please God, to minister to God's people for the sake of God's elect by doing His will.
8 And I heard the voice of the Lord saying, “Whom shall I send, and who will go for us?” Then I said, “Here am I! Send me.” 9 And he said, “Go, and say to this people:“‘Keep on hearing,  but do not understand;
keep on seeing,  but do not perceive.’
10 Make the heart of this people dull, 
and their ears heavy,
and blind their eyes;
lest they see with their eyes,
and hear with their ears,
and understand with their hearts,
and turn and be healed.”
11 Then I said, “How long, O Lord?”
And he said:
“Until cities lie waste
and houses without people,
and the land is a desolate waste,
12 and the Lord removes people far away,
and the forsaken places are many in the midst of the land.
13 And though a tenth remain in it,
it will be burned  again,
like a terebinth or an oak,
whose stump remains
when it is felled.”
Yet God makes clear Isaiah will declare salvation but see very little to show for it. His preaching will harden hearts. People will ignore the call to repent and go merrily to destruction. Yet even so, God will preserve His people. He will call forward His elect through the preaching of His Word, just as He did with Isaiah, through the preaching of his glory by the seraphim.
Preaching will precede judgment and exile, but after exile an elect remnant shall return to the Promised Land. This was true of national/ethnic Israel in the Babylonian captivity, and it is true of Christ's church in spiritual Babylonian captivity.
We are saved by grace and called to proclaim that salvation to others by God's grace. Many times our hearts will be broken as call after call to repentance will go unheeded by most, but our call remains, as it did for Noah, who preached for 120 years while building the Ark but saw no converts from it (2 Peter 2:5).
Even so, like Isaiah we can rejoice that all the Lord has called to salvation will be saved, that faith that justifies comes by hearing and hearing by the preaching of Christ (Rom. 10:17), and that not one jot or tittle of God's Word will return to Him void; it will accomplish what it was sent forth to do (Isa. 55:11).
Soli Deo gloria!