At his second Senate Judiciary Committee today, Judge Brett Kavanaugh "affirmed" that his testimony would be true. Usually the word used in swearing in is "swear."
So why did Senator Grassley use the word "affirm" when swearing in Brett Kavanaugh?
The Constitution allows the President to take the oath of office by either swearing or affirming. By extension, any person coming before Congress or a court may also swear or affirm to tell the truth.
The reason for the two options is because of what Jesus said in Matthew 5:34-37: "But I say to you, make no oath at all, either by heaven, for it is the throne of God, or by the earth, for it is the footstool of His feet, or by Jerusalem, for it is the city of the great King. Nor shall you make an oath by your head, for you cannot make one hair white or black. But let your statement be, 'Yes, yes' or 'No, no'; anything beyond these is of evil."
Jesus expects his followers simply to tell the truth. Swearing that a statement is true implies that other statements not sworn to may be false. But citizens of God's Kingdom should live up to God's standards. Yes means yes, and no means no.
As a follower of Jesus, if I am called by a court to testify, I will choose to affirm—not swear—to tell the truth. Telling the truth does not require a swearing, but simply an affirmation that statements are truthful.
I do not personally know whether Judge Kavanaugh has made a similar decision with regard to the oath that he took today. But my suspicion is that he did. He purports to go to church every Sunday, and he seems to have a long history of faith in God.