Diodorus Siculus 17.110.6-8
6 [A]fter a stay of thirty days he resumed the march and on the seventh day came to Ecbatana of Media. 7 They say that its circuit is two hundred and fifty stades. It contains the palace which is the capital of all Media and storehouses filled with great wealth. Here he refreshed his army for some time and staged a dramatic festival, accompanied by constant drinking parties among his friends. 8 In the course of these, Hephaestion drank very much, fell ill, and died. The king was intensely grieved at this and entrusted his body to Perdiccas to conduct to Babylon, where he proposed to celebrate a magnificent funeral for him.