To understand Jesus’ teaching about sexual sin, we must first consider what the Bible says about sex and marriage. For that, we shall turn to the opening chapters of the Bible: “On the sixth day of creation, God said, ‘Let Us make man in Our image, according to Our likeness…’ So God created man in His own image; in the image of God He created him; male and female He created them… Therefore a man shall leave his father and mother and be joined to his wife, and they shall become one flesh” (Genesis 1:26, 27; 2:24). In some way that we cannot fully understand, God is both one and more than one; that is why He can say, ”Let Us create man in Our image.” This unity/plurality is evident even in the first chapter of Genesis. For example, the Hebrew word translated “God” is a plural form, but it takes a singular verb (such as “created” in 1:1). Likewise, the Spirit of God and the Word of God both appear in the process of creation (1:2,3; 2:7; etc.). In the New Testament, these hints of a unity and plurality in God become the clear statements that God is Father, Son, and Holy Spirit – one God, yet somehow three. Likewise, man is both one and more than one, man and woman in one unity called “man.” Thus, it seems that part of the image or likeness of God is our unity and plurality. We are two – male and female, man and woman – and yet we are one “man.” In marriage, this unity becomes visible: “The two shall become one flesh.” Marriage, therefore, and especially sexual relations within marriage, reflects the image of God in man. Furthermore, in many passages in the Bible, God is pleased to refer to Himself as husband of His people (the classic text is Ephesians 5:22 –33, but there are more). That is another reason why marriage is central to God’s plan for the world, and why sex within marriage receives so much emphasis in God’s Word. In short, sex is sacred because it expresses and strengthens the unity of two persons created in the image of God, who is Himself both one and more than one. And sex is sacred because marriage itself is sacred.