The answer is: Camel's hair

Matt 3:4 - A rough and coarse garment like the prophets used to wear. c.f. Zec 13:4; 2 Ki 1:8

John the Baptist was definitely a larger-than-life figure, and his choice of wardrobe tells us a lot about him. Wearing a garment made of camel's hair not only set him apart but also resonated with the tradition of the prophets in the Hebrew Scriptures. This wasn’t just a quirky fashion statement; it acted as a symbol of his rugged lifestyle and unwavering dedication to his prophetic mission.

Think about it: camel’s hair tends to be tough and durable, much like John’s fierce and unyielding message about repentance. You might recall that prophets like Zechariah and Elijah were often depicted in similar attire, presenting an image of timeless rallying against social laziness and moral complacency. This aligns them with others who dare to challenge the status quo.

Interestingly, the prophet Zechariah pointedly notes that in the coming days, false prophets would be ashamed of their garments of camel’s hair and would instead wear softer clothing– this gives us a fascinating peek into how prophetic identities were perceived in contrast to societal norms.

Also worth noting is how John's austere lifestyle, marked by his ascetic diet of locusts and wild honey, reflects the essence of many ancient spiritual practices. Without the distractions that luxury brings, he was determined to remain focused on his higher calling. Isn’t it remarkable how Biblical stories are always full of rich layers asking us to dig a little deeper?!