The answer is: David

2 Sam 11:14 - He wrote it to Joab

The first letter mentioned in the Bible comes from an unexpected place—King David himself. In 2 Samuel 11:14, while orchestrating the demise of Uriah the Hittite, David reveals not just his desperation but a letter sending Joab hypothetical instructions which would lead to tragic consequences. It’s interesting to see how this act of writing isn’t just about penning a note—it's a reflection of power dynamics and moral complexity.

Psalm 51, one of David's most famous psalms, offers a notable echo of his inner turmoil during this time. After sinning with Bathsheba and orchestrating her husband's death, David reflects on his guilt. This combination of David as a skilled king yet a flawed individual serves as a poignant reminder of the nuances of leadership.

You might wonder about the medium of the letter. In biblical times, letters were often carved into clay or written on parchment using reed pens and ink—a testimony to ancient communication’s artistry. Also, consider that David not only wrote the first letter but established the role of messenger, having Uriah deliver the letter—witnessing his own fate, unknowingly bearing his destruction.

Letters in the Bible serve myriad purposes, and David's tragically sets the tone for the complexities of human relationships through the Scriptures. So, as we reflect on this, let's contemplate the powerful legacy of both words and actions.