"But Jesus never said ________" (you fill in the blank). Far too often, an appeal of this type is made in conversations in order to help support one's point of view. I have heard this line of reasoning most commonly invoked in regards to the debate over homosexuality. For instance, a homosexual advocate might say "Well you know, Jesus never said anything about homosexuality." And since Jesus never said anything about it, it is therefore concluded that there is nothing really wrong with the behavior. After all, if it was really bad, Jesus would have said something, wouldn't He? If only it were that easy.
First, it must be pointed out that this type of reasoning is fallacious. In logic this is referred to as an argument from silence. For example, suppose I were to say "Well, John never said he wasn't a psychopathic homicidal maniac...that must mean he really is one!" Notice that my "proof" that John is a serial killer comes from a total lack of support either way. I am attempting to make an argument from a lack of evidence. In the same manner, Jesus' lack of commentary on homosexuality proves nothing, which brings us to our second point.
Second, Jesus didn't say a lot of things. He never said spousal abuse was wrong or that torturing toddlers is immoral. He never said it was wrong to intentionally trip a blind person or make fun of the hearing impaired. Are we to conclude from this that there is nothing wrong with these acts simply because "Jesus never said?" If the "Jesus never said" argument proves anything, it proves too much!
Finally, in regards to the homosexual debate, Jesus actually did say something! He just didn't say it in the Gospels. Jesus claimed to be the "I AM" of the Old Testament (John 8:58). And in the Old Testament, YHWH clearly makes His view of homosexuality known (Lev. 18:22). Furthermore, according to 2 Timothy 3:16, all Scripture is inspired by God. Meaning that it is not just what Jesus said in the Gospels that we need to take heed to. And, by the way, if all Scripture is God-breathed, and Jesus is God, that means all of the words contained in the Bible are the words of Jesus (not just the words in red!) So, even the New Testament prohibitions against homosexual behavior (Romans 1) can be attributed to Christ.
So the next time someone responds to you by saying "But Jesus never said..." you might want to follow the example of Francis Beckwith when he quipped, "Jesus never said that you should only believe the things that Jesus said."