The answer is: Oaths

Matt 5:36

In Matthew 5:36, when Jesus stated that one cannot make a single hair on their head black or white, he was really honing in on the larger theme around oaths and binding promises. He was expressing the impossibility of controlling the minutia of life, much less the weighty matters of truthfulness and integrity. Over and over again, the teachings of Jesus draw attention to our tendency to rely on external affirmations, like oaths, to validate our words. It's like he's nudging us to appreciate that our reliability and honesty are intrinsic, independent of promises backed by divine power.

Fun fact: did you know that using images of hair in Hebrew literature is also prominent in the militant Psalms? It’s almost poetic how weaves of themes connect throughout the Scriptures. Moreover, ancient cultures often held hair to have mystical significance—a symbol of one's vitality. In saying someone's hair cannot be changed by one's word, Jewish thought might echo the idea that depth and authenticity travel beyond the superficial control of appearances.

Jesus crafts a radical call to truthfulness that says, "Hey, before you pick up ancient ways of promise-making to establish your credibility, just be credible! Live a life so aligned with truth that no promise is ever necessary.” By pointing out this insignificant point, He raises gigantic issues of authenticity and character, giving us a refreshing challenge to think deeply about how we express truth today.