Lately, I have been reading about people wanting to know where in the Bible does Jesus, himself only, state that same-sex relationships/marriages are a sin. They claim only Paul said that they are, not Jesus. Also, these people claim that we are not obligated under any of the Levitical laws now, and that would include same-sex relationships. Why are some laws in Leviticus not applicable to us now, but others are?
Everyone who understands that the Bible is the inspired word of God (2 Tim. 3:16) knows that regardless of which one of its 40 writers wrote down the words, every one of those words, from Genesis 1:1 through Rev. 22:21 originated with God. Therefore, words attributed to Paul carry the same weight as those attributed to Jesus. In some cases it’s obvious from the context that the Lord has a particular audience in mind, but without clear evidence to that effect we should assume everything we read there is meant for us.
Some of the Levitical laws were teaching tools aimed at demonstrating to Israel the importance of maintaining a separate lifestyle from the world. Others were health and cleanliness related. Many of these no longer have application to us.
But a surprising number of acts prohibited in the Old Testament are also prohibited in the New Testament. Adultery, sexual immorality, incest, homosexuality, divorce, theft, murder, slander, false witness, blasphemy, idolatry, drunkenness, and gluttony are just a few examples. These things were sins from man’s earliest times and they are still sins today.
As for the specific sin you mention, the prohibition against same sex relationships can be found in both Leviticus 20:13 (Old Testament) and Romans 1:26-27 (New Testament). The fact that Jesus didn’t mention that particular sin does not mean we can ignore what the Bible says about it.