“Jesus said to his disciples: "You have heard that it was said to your ancestors, Do not take a false oath, but make good to the Lord all that you vow. But I say to you, do not swear at all; not by heaven, for it is God's throne; nor by the earth, for it is his footstool; nor by Jerusalem, for it is the city of the great King. Do not swear by your head, for you cannot make a single hair white or black. Let your 'Yes' mean 'Yes,' and your 'No' mean 'No.' Anything more is from the Evil One.” -Matthew 5:33-37
If we accept and live in God's grace, then let our actions in life be our vow of truth. If we are truly living in Christ for all to see, there is no need for anyone to ask about our sincerity or honesty; our commitment to Truth is readily apparent.