Our Constitution never refers to the Bible.
You're not thinking.
The Constitution also never refers to marriage. And it's no surprise that the Constitution never refers to the Bible or marriage. This is because the mostly Christian Founding Fathers (<-click) wrote the 10th A. so that government powers not enumerated in the federal Constitution are automatically reserved for the states.
10th Amendment: The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.So the states have the power to not only outlaw gay marriage according to the will of a state's majority voters, but also to teach the Holy Bible in public schools. This regardless of the USSC's perversion of Jefferson's "wall of separation," but provided that people's 14th A. protections are respected.