Flavius Arrianus (c. 86 CE – 160 CE) was born in Nicomedia, the capital of Bithynia (now in modern Turkey). Arrian had a distinguished career in Rome, being entrusted with high political offices, achieving the office of consul under Antoninus Pius at his peak. His Discourses of Epictetus was written c. 108.
The following is an adaptation of The Life and Writings of Arrian, trans. Edward J. Chinnock, 1893.
§ 3. On the third day after the battle, Alexander reached the river Ister [Danube], which is the largest of all the rivers in Europe, traverses a very great tract of country, and separates very warlike nations. Most of these belong to the Celtic race, in whose territory the sources of the river take their rise.
§ 4. There ambassadors came to him from Syrmus, king of the Triballians, and from the other independent nations dwelling near the Ister [Danube]. Some even arrived from the Celts who dwelt near the Ionian gulf. These people are of great stature, and of a haughty disposition. All the envoys said that they had come to seek Alexander’s friendship. To all of them he gave pledges of amity, and received pledges from them in return. He then asked the Celts what thing in the world caused them special alarm, expecting that his own great fame had reached the Celts and had penetrated still further, and that they would say that they feared him most of all things.
But the answer of the Celts turned out quite contrary to his expectation; for, as they dwelt so far away from Alexander, inhabiting districts difficult of access, and as they saw he was about to set out in another direction, they said they were afraid that the sky would some time or other fall down upon them. These men also he sent back, calling them friends, and ranking them as allies, only adding the remark that the Celts were braggarts.