In the Gospel Jesus told us to avoid swearing to the truth of what we have done. He said,
“Let your “yes” mean “Yes,” and your “No” mean “No.”
I associate that with two verses from Chapter One of John’s Gospel.
Verse 17: “While the law was given us through Moses, grace and truth came through Jesus Christ.
What a fine summary of the manner of Jesus. Through and through he was gracefulness and he was truth.
The other incident is from verse 47. When Jesus saw Nathanael coming toward him he exclaimed, “There is no duplicity in him!”