What is an example of God using one's friends to bring a person to salvation?

Marcus Serven explains in this video that he was saved when he was 17. He was raised in a Christian home but he was clueless to understanding what sin, repentance, and the grace of Gospel involved. 

He remembers arguing with pastors about the validity of Christ's claims. His friends at school cornered him one day. They had each attended a camp where the speaker challenged them to share the Gospel with one person. They all decided to talk to him. 

God had already been preparing his heart and convicting him of sin. At that time, he was ripe for hearing the Gospel. His friends talked to him about the Gospel. His friends talked to him about Revelations 3. He realized that he was like the Church of Laodicea -- he wasn't for God or against him.  

Revelations 3:15-16 (NKJV) - "I know your works, that you are neither cold nor hot. I could wish you were cold or hot. So then, because you are lukewarm, and neither cold nor hot, I will vomit you out of My mouth."

Yeah, as for myself, I came to know the Lord when I was 17. Like so many people, I was raised in a Christian home, but I really was pretty clueless when it came to understanding what sin and repentance was, and I surely didn't understand the grace of God in the gospel. So we attended church. I remember arguing at times with the different pastors there about the miracles and about the validity of Christ's claims. But it was some of my friends, some buddies at school who cornered me one day and they told me later they had gone off to a camp over that weekend where the speaker had challenged them all to prayerfully consider who they could share the gospel with when they came home.

So these three friends, all unknown to one another, had all come to the realization that they were going to share the gospel with me and when they shared that with one another they decided to work together. So I remember going to school that day in March of 1971 God had already been preparing me. He had been convicted me of a number of sins. I had had these discussions, lengthy discussions with pastors at our church and I was very much ripe for hearing the gospel and my friends began to take me to the Word of God, to show me my need for repentance, to talk about what faith in Christ really meant, what the claims of Jesus were upon my life. And finally, after maybe two or three months of just a repartee back and forth, they finally took me to Revelation chapter 3 where it talks about the message to the church of Laodicea.

And if you recall, our Lord says of that church that you are neither hot nor cold and so because of that I spit you out and I realized that was describing me. I was the church of Laodicea, Not literally of course, but figuratively that was describing me. I was neither for him nor was I against him. I was lukewarm as could be and it was the time for me to make some kind of commitment. Either I was going to receive Him and follow Him the rest of my life or I was going to reject Him.

And under the conviction of my sins, I remember praying late that night that I would receive him, that I would follow him for the remainder of my life.