Daniel Hyde Writes:
The Thessalonians were converted, and so they turned to God; they were changed by God, and so they turned to him with a changed lifestyle; they were restored by God unto him from idols, so they could be described as having turned from idols to the Lord.
This change in direction led to a change in affection. Because of what God did to turn them they began to serve the living and true God, and to wait for his Son from heaven (vv. 9–10). The implication is that before they served the living God they served a dead god. Before they served this true and genuine God, they served not false gods, as though there is one among many, but they served unreal, imagined gods. And so they were changed, they were turned and as the result of this change and turning from the greatest idol of all, which is self, they had come to serve God, and to wait for his Son from heaven.
It was not just the mind that was changed, not just the will, in which we are able then to choose, and to do, and to follow a path and a course of life; but the affections were changed. This is the deep-rooted aspect of our being. They are the things that we long for most, that we admire the most, and that we love the most. They are not really emotions, as that is one aspect—but it is that quality of our humanity that loves, and that longs and desires for something. This has been changed as well. Christ has healed our wills, our minds, but also our affections. And having done this we even more and more constantly pray that Christ would turn us even more in our day-to-day lives towards these things, to serve and to wait.
Recall the story of Jesus’ temptation in the wilderness. Our Lord’s final temptation was that the devil brought him up to a high point to show him all the kingdoms of the earth in all their glory. The devil then says, “These all I shall give you if you will only serve, bow down and worship me” (Matthew 4:9). Our Lord Jesus Christ, amazingly being God in the flesh, cries out and rebukes the devil with the words of the book of Deuteronomy: “You shall worship the Lord your God, and Him only shall you serve” (Matthew 4:10 cf. Deuteronomy 6:13). Throughout Deuteronomy there is another verb that is added on to that service of the one true God: “cleave” or “cling.” We are to cling to this one true God, to serve this living God, to cleave to this true God, who has revealed Himself to us in Christ. We were saved that we might serve.