The first ever consumption of cannabis was recorded as Chinese Emperor Shen Nung discovered the medicinal properties of cannabis around 2700 BC. About 1000 years later, in 1500 B.C., the Chinese Pharmacopeia had the earliest written reference to its medicinal properties like Shen Nung had discovered.
Places such as Egypt, India, and the Middle East all soon discovered the medicinal properties of cannabis. Egyptians were using cannabis for treating glaucoma, inflammation and enemas in 1213 BC. In 1000 B.C., India used bhang, which is a mixture of typically milk and cannabis, and used it as an anesthetic and anti-phlegmatic. An ancient Persian religious text mentions bhang and also lists cannabis as the most important of 10,000 medicinal plants. (Source of facts taken from Herb.co)