I understood that Christians were not to swear to any oath. During baptism, parents respond to questions about raising their child in the church with "I do." Is this an oath?
Matthew 5:33-37 addresses oaths as a form of seeking to guarantee the truthfulness of a claim you are making by referring to an authority beyond oneself, such as the temple.
Jesus calls his disciples to speak plainly and truthfully always, and so never to seek to bolster or guarantee their truthfulness by claiming some higher authority for it.
At baptism, marriage and ordination, plain-speaking is exactly what we are called to do. We "vow" (promise) simply and directly that we affirm or will do what is asked of us. And then we seek to continue to do those things. No oath (guarantee of truthfulness by reference to some other authority) is involved.
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