Take a quick look at the inscription of the charge against Jesus on the Cross. It is specifically mentioned in all four of the Gospels. But if you look closely, it is different in each one. Two of them mention that it is in three languages, but the other two do not. If you only read one of the passages, you may not learn that it was in three languages. And if you only read one passage, you may come away with the idea that it was the soldier's idea to write the charge, when in reality it was Pilate who commanded the charge to be written. And there are other differences as well.
My point is, that if we only look at a few passages and exclude others from our research, we may get a skewed idea about what Scripture really says about a subject. Yes, we are commanded to believe, but if we stop with just the passages that say believe, we may miss other passages that command repentance as well, and also confession of Jesus' Name, and also immersion. All must be done, or none of them have meaning.