The source of social proof is crucial for its credibility and effectiveness. You want to use sources that are trustworthy, reliable, and relatable to your audience. For example, if you want to persuade someone to try a new restaurant, you could use social proof from a reputable food critic, a friend who has similar tastes, or a large number of satisfied customers. You should avoid using sources that are biased, dishonest, or irrelevant to your audience. For example, if you want to persuade someone to vote for a candidate, you should not use social proof from a paid spokesperson, a rival party, or a random stranger.