The answer is: Oaths

Matt 5:36

In Matthew 5:36, Jesus extends the conversation on oaths to highlight our limitations as human beings. By stating that we can't change one hair on our head from black to white, He emphasizes the futility of relying on our promises or trying to manipulate the truth of our situations with grand declarations. Instead, His teaching points us toward reliability in our everyday speech. It's a reminder that honesty should be inherent, not contingent on dramatic oaths or vows.

Isn’t it interesting to note that hair turns grey or white over time but not back again? This reflects the natural progression of life, and just like our mortal bodies change, so should our words—to become more truthful, simple, and direct.

Moreover, in Biblical times, oaths were taken especially seriously. People would often invoke a higher power or use elements of nature to back their promises, which meant that breaking these oaths was viewed as deeply dishonorable. This connection to nature, including something as seemingly trivial as our own hair, serves to ground Jesus' point: what we present in our lives matters more than the weight of promises or oaths.

The broader context of Matthew 5 includes encouragement for authenticity and drawing attention to the power of our simple affirmations—letting our 'yes' be 'yes,' and our 'no' be 'no'. So ultimately, Jesus encourages us to embrace sincerity each day and express integrity through our actions, not just our words.