Your pastor was probably quoting from the New Testament: "Without holiness no one will see the Lord" (Hebrews 12:14). But this doesn't mean it isn't enough to believe in Jesus in order to be saved. In fact, the opposite is the case.
Let me explain it this way. Suppose you were a farmer working in your fields. It had rained the day before, and by the end of the day you were filthy and your clothes were covered with mud. (I grew up on a farm, and I know how easily this could happen!) Then suppose that when you came home your wife told you the governor had invited you for dinner that evening. But you knew that if you showed up in your dirty clothes, you'd be turned away—and when you went to your closet, everything else was dirty also. But then suppose the governor's chauffeur drove up, and brought in a spotless suit of clothes that fit you perfectly! Now you could appear without embarrassment at the governor's dinner.
This is a homely illustration, I know—but this is what Jesus Christ has done for us. We have no holiness of our own; as the Bible says, "All our righteous acts are like filthy rags" (Isaiah 64:6). But when we come to Christ, God takes those rags away, and He clothes us instead with the perfect holiness of Christ. Yes, without Christ's holiness we'll never see God—but with it we will! Thank Him now for this great truth.