Although the First Amendment of the U.S. Constitution declares:
"Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances."
Christian Bibles are sometimes used in Courts to swear an oath.
In contrast to the tradition of swearing by the Bible, we are told in Matthew 5:33-37:
[33] “Again, you have heard that it was said to the people long ago, ‘Do not break your oath, but fulfill to the Lord the vows you have made.’ [34] But I tell you, do not swear an oath at all: either by heaven, for it is God’s throne; [35] or by the earth, for it is his footstool; or by Jerusalem, for it is the city of the Great King. [36] And do not swear by your head, for you cannot make even one hair white or black. [37] All you need to say is simply ‘Yes’ or ‘No’; anything beyond this comes from the evil one."
If Matthew 5:33-37 is literal, why would Christians swear an oath on the Bible?