The answer is: Oaths

Matt 5:36

In Matthew 5:36, Jesus makes the poignant point that we cannot control the basic facets of life, like the color of our hair. It’s a clever way to remind his listeners—who were perhaps overly focused on the consequences of their words and oaths—that calling upon God to validate our speech can be fruitless. Essentially, we shouldn't resort to elaborate oaths, as our speech should hold integrity and truthfulness without the need for extra flourishes.

This line also echo the broader theme of honesty prevalent in Jesus' Sermon on the Mount, where he invites us to stick to plain 'yes' or 'no' instead of embellishing into solemn promises or complicated terms. Irony resides here; it highlights humanity’s tendency to exert control over aspects of our lives we could never genuinely manage.

Interestingly, hair has cultural and symbolic significance in many societies. In biblical terms, hair can reflect dignity and status; think of the long locks of Samson, which symbolized his strength. But not all context holds reverence—think of moments in Mark where people sought healing through the means of Jesus’ clothing.

As we digest such verses, it's clear that sometimes wisdom lies not in glib affirmations, but in the quiet understanding that sincerity, not grandeur, is our greatest gift. The simplicity of being genuine allows a world so focused on promises to engage in authentic connections instead.