The answer is: Oaths

Matt 5:36

When Jesus mentions the impossibility of changing one hair on your head from black to white in Matthew 5:36, he's diving deep into the themes of integrity and truthfulness. In that part of the Sermon on the Mount, Jesus brings our attention to the futility of boasting about our ability to control the smallest details of life, like our hair color. It's a clever illustration; after all, all of us have some control over our style choices but none over our inherent features.

This raises an interesting backdrop: in ancient cultures, making oaths was a serious business, often tangled up with a person’s honor and societal standing. People would invoke not just their own name but the name of God or sacred elements. When Jesus calls out the practice of swearing oaths, He's emphasizing a call for honest, straightforward communication without the theatrics of binding vows.

Moreover, if we think of the symbolism behind hair in Judeo-Christian traditions, it often associates with one's identity or fate. This talk of hair can echo stories from the Old Testament, like the infamous Samson, whose strength lay in his uncut hair.

The core message here is really about authenticity; Jesus encourages us to embody truth so fully, that we need not adorn our words with fancy oaths. Every utterance can be a testament to who we are, trusting that honesty speaks louder than any boastful promise.