Following the affliction of God's people and the death of God's servant, 55:1-3 proclaims a life of abundance, an everlasting covenant that is predicated on listening to God, which brings life. The reigning line of King David, a promise God made to him, is here talked about being continued, the Davidic dynasty that the servant is a part of. This servant is a witness/leader/commander to/for the peoples (again, plural, more than just Israel) and Israel will call to, and receive, an unknown nation because of this servant and because the Lord Israel's God has glorified her (5). In vs. 6-7 God the Word encourages the reader/hearer to seek the Lord, call on Him, and turn from unrighteous ways to return to the Lord. God's compassion will cover those that do and God will not just pardon, but abundantly pardon! The rest of the chapter beautifully tells us how great the mind of God is (with thoughts and ways far above our own), how indefatigable His Word is, and how all of creation will be transformed by the Word. Again, keeping it in context, the Word that is speaking is the God that will one day be the servant of God, as the Word has always gone out to accomplish what God wills.
Call upon Him while He is near.
Let the wicked forsake his way
and the unrighteous man his thoughts;
And let him return to the Lord,
And He will have compassion on him,
And to our God, for He will abundantly pardon."
I only stop here for space's sake, but would love to carry it out until verse 11. God is now, as then, calling all people to repentance, to turn to Him and receive His offer of pardon. The language brings to mind the penal system, that of crime followed by just punishment. God is not, as Bruce Almighty might say in a moment of impassioned pain, up there waiting for the opportunity to "burn our feelers off." He wrote the book on truth and could easily let the truth damn us all, but our great God provides pardon. He wants to provide pardon, and so He calls to us and tells us that we need to seek for, and call on, Him. As verse 11 states, His word doesn't return to Him without first accomplishing what He desires, the reason for which it was sent.
So we, then, have possibly only one of two options for interpreting this clear statement: we can believe that God purposes for all to be enveloped in His compassion, no matter their response to the commands of verses 6 & 7, on the one hand, or that there are only certain ones whom God has deemed worthy to receive His compassionate pardon on the other; or that the purpose of God's word is to welcome all who would respond to verses 6 & 7, and it will accomplish just that. Option 1 has two parts that are different in their essence: Part 1 seems a beautiful possibility that leaves no one out of God's blessing, everyone is included, and we might say that this is what you would expect from a loving God; Part 2 seems restrictive, almost malevolent, in the sense that some are removed from the blessing right out of the "birthing gate," and is not what you would expect of a loving God.
What both parts have in common, however, is that they invalidate the commands of 6-7, to seek, call, forsake, and return. These are not things to say to those who have no say in the matter. Is God saying, "You who have no choice, choose anyway, as though it mattered, which it doesn't" to us? And we should consider whether it is loving at all to have humankind rolling around in the quagmire of earth's pain and evil right now if God's coming compassion to all or some is preordained. This might be a level of meaningless not even Solomon imagined. But most importantly, we will find ourselves in the awkward position where we ask of the text, "which of these verses are true, and which are not?" We do not see in this text that God wants us to turn from our wicked ways and live (specifically) but the repetition of this refrain in scripture is true, nonetheless. So Option 1 causes us to "play God," determining which verse is authoritative, and which isn't.
Though some struggle with the term "free will," verses 6-7 hold the term implicitly. So Option 2 alone allows both of these texts to be true, both to be authoritative. God's Word accomplishes what He has purposed, namely that it sets before people life and death and they respond to it, and in some cases the Word stands as a testimony to those uniquely purposed to serve as the instrument of God's will, made for holy or common purposes. The choice is not either/or but both/and. God's purpose is to draw all to Himself, not by force or without the will to choose life or death. I do not get, from the full scope of scripture, a God who dangles a carrot, content to take it away as He pleases. Rather, He holds it out to us imploringly, begging us to eat and drink without cost (55:1). God's greatest gift of salvation is great only if we are allowed the choice to hunger and thirst after righteousness. If some are not hungry, we cannot force them to eat.