What is the call of the gospel ? Christ explicitly delineates the evangelical call as directed exclusively to His sheep, who are the predestinated, chosen of God and this call is soteriologically efficacious : "he calleth his own sheep by name and leadeth them out" John 10:3 : He leads them out of the Lake of Fire into everlasting habitations of redeemed sinless glory with the Father. Christ asserts that the spiritual name of these sheep are "sinners" - that is, those who know they are sinners by the regenerating grace of God : they are sensible sinners - as those who know they are sick - they hunger and thirst for righteousness. For apart from God's efficacious grace all men are self righteous and presume to be able to save themselves by a psychological, spiritual or physical act of their will : salvation is presumed to be conditional - a quid pro quo on some level. Without controversy those who are called shall be glorified - Romans 8:30. The call of the gospel is the call to repent and believe in the glad tidings FOR YOU - and there are only glad tidings for the elect - only the elect are called by Christ to come to Him repenting and believing the gospel.
Isaiah 1 suggests that Jerusalem is SODOM and GOMORRAH but for a very little remnant : and Jerusalem at the end of the chapter is burned up, purged as by a refiner's fire, as Christ shall judge the world on the Last Day, and out of it comes the cleansed and redeemed people of God - however, not until this Assembly of the elect is castigated as having gone their own way (note throughout Isaiah 1) unto a thorough rejection of Him and a love of self and self satisfaction, indeed unto a refusal to look after the poor and needy, that is, unto a refusal to evangelize the true gospel is the purging instantiated (see Isaiah 1:21ffz). However, following the apostasy - the faithful city of Jerusalem becoming the Harlot (Isaiah 1:21) of Revelation 17 and 18 (cp. Revelation 17:1), and the subsequent purging and taking away of the filth of her sins, the LORD establishes her above all mankind, exalting her as a beacon to the elect from every nation (Isaiah 2:2ff) whereupon she by the grace of God shall fulfill the duty to evangelize and so MANY shall be brought in from all nations - the Jerusalem (the elect) as the "very small remnant" Isaiah 1:9 is also Jerusalem the "many people" (Isaiah 2:3) as in Matthew 22:1-14 "Many are called" (as in Isaiah 2) / but "few are chosen" (as in Isaiah 1) - the Assembly of God is simultaneously few and many depending on the perspective taken : few compared with the population of the world , many in its own right as it represents some from all nations - some who are not called , who do not regard themselves as sinners (in the sense of completely unable to save themselves by an act of their will) but seek the glories of Christ's shed blood earned heaven for sinners notwithstanding (who are most likely those who claim the name of Christ as members of his external church but are not of the eternal church) , when they attempt to come to Christ on the basis of an act of their own will, Christ casts them out into everlasting fire - saying I never knew you.