Relationships are not necessary, as testified by the Scriptures: If it’s always better to build a relationship before sharing the gospel, the apostles really missed the boat. In Acts 2, Peter stood up and shared the gospel with thousands of people he didn’t know. In Acts 17, Paul set up shop in the marketplace in Athens and “reasoned” about Christ with “those who happened to be there” (Acts 17:17). And then when he was called before the Areopagus council Paul stood up and preached the gospel to a whole group of cultural leaders he’d never met (Acts 17:19-34).
Relationships can help: Is it never an advantage for someone to know you personally before you share the gospel with them? Of course not. It’s a great idea to get to know someone and learn what idea of Christianity they might already have. It also gives them a chance to see that your life stands out, that you’re different from other people they know, prompting them to wonder what makes you different.
Bottom line: relationships with non-Christians can enhance our evangelism and create opportunities for evangelism, but they aren’t necessary for evangelism.