“What man among you, if he has a hundred sheep and has lost one of them, does not leave the ninety-nine in the open pasture and go after the one which is lost until he finds it? When he has found it, he lays it on his shoulders, rejoicing. And when he comes home, he calls together his friends and his neighbors, saying to them, ‘Rejoice with me, for I have found my sheep which was lost!’ I tell you that in the same way, there will be more joy in heaven over one sinner who repents than over ninety-nine righteous persons who need no repentance.”
One member of The Society of Evangelical Arminians writes: “In this verse, the ‘sinner’ almost certainly means an unregenerate non-believer, and there is rejoicing in heaven because that person has repented. So a non-believer can do one thing that pleases God--repenting.” (SEA)
Calvinist, Erwin Lutzer, writes: “Calvinists believe that election makes the success of God’s plan certain. God has committed himself to save a certain number, and they will be saved, despite the rebellion of mankind. The unbelief and failure of man can never thwart the intended plan of God.” (The Doctrines That Divide, p.213, emphasis mine)
Calvinist, George Whitefield, writes: “I believe the doctrine of reprobation, in this view, that God intends to give saving grace, through Jesus Christ, only to a certain number, and that the rest of mankind, after the fall of Adam, being justly left of God to continue in sin, will at last suffer that eternal death which is its proper wages.” (A Letter from George Whitefield to the Rev. Mr. John Wesley, emphasis mine)
Calvin explains: “But, how does he say that the repentance of one ungodly man yields greater joy than the perseverance of many righteous men to angels, whose highest delight is in a continued and uninterrupted course of righteousness? I reply, though it would be more, agreeable to the wishes of angels (as it is also more desirable) that men should always remain in perfect integrity, yet as in the deliverance of a sinner, who had been already devoted to destruction, and had been cut off as a rotten member from the body, the mercy of God shines more brightly, he attributes to angels, after the manner of men, a greater joy arising out of an unexpected good.” (Parallel Classic Commentary on the New Testament, p.252, emphasis mine)