Bacchylides - b.510BC, fl. 485-450.

Epictetus - 2nd Cent.

There are enough irksome and troublesome things in life; aren't things just as bad as the Olympic festival? Aren't you scorched there by the fierce heat? Aren't you crushed in the crowd? Isn't it difficult to freshen yourself up? Doesn't the rain soak you to the skin? Aren't you bothered by the noise, the din, and other nuisances? But it seems to me that you are well able to bear and indeed gladly endure all this when you think of the gripping spectacles you will see.

Herodotus. Histories, book 8.59

"Themistocles," [Adeimantus] observed, "in the races, the man who starts before the signal is whipped." "Yes," was Themistocles' retort, "but those who start too late win no prizes."

Pausanias. ca. 175AD. Guide to Greece, book 5 & 6

Philostratus. On Gymnastics.

The pankratiasts . . . practice a dangerous brand of wrestling.  They have to endure black eyes, which are not safe for the wrestler, and learn holds by which one who has fallen can still win, and they must be skillful in various ways of strangulation. They bend ankles and twist arms and throw punches and jump on their opponents.  All such practices are permitted in the pankration except for biting and gouging.

Pindar - b.518BC, active to 446BC. Olympic Odes

Plato

I list here various ancient writers and the name of their work. I quote those who make a passing reference to the games. Consult the listed works for longer essays.