The opening of Homer's Iliad. The god Apollo sends a plague upon the Achaean army.

This is the opening of Homer's great epic poem The Iliad.
Sing muse, sing the wrath of Achilles, that brought so much suffering on the Achaeans and tore many brave souls from their breasts, sending them to Hades, the darkest of caves, their limbs torn by birds and dogs.
All this was according to the will of mighty Zeus.
It all began with strife between Agamemnon, King of Men, and the godlike Achilles, son of Thetis. Enraged at an insult to his priest Chryses, Apollo put aside his lyre, took up his bow and aimed deadly arrows against Agamemnon and his men. He sent a plague against the army and, one by one, the soldiers began to die.
It was not long since Chyrses, priest of glorious Apollo, had walked down to the ships to buy, with priceless gifts, his daughter’s freedom, for Agamemnon had seized her as his prize. He held the golden sceptre and crown of Apollo and spoke to all, but mostly to the leaders Agamemnon and his brother Menelaus.
Stretched out on the beach, where the funeral pyres would soon smoulder, the army gathered.
Chryses began to speak.
Great sons of Atreus, and all well-armoured Achaeans, may the gods grant you success in your siege of Troy and give you safe passage home. Win the blessing of Zeus by honouring his son Apollo. Take this fitting ransom for my daughter.
The men acclaimed the priest, reverencing him and his gifts, but Agamemnon was of a different mind. He violently abused the priest. “Stupid old man, go, and never again return, or your crown and sceptre will not save you. Your daughter will be mine until she dies. In our court at Argos, far away from her beloved homeland she will spin and weave and prepare with all fit ornaments my bed.”
Silently the priest walked away, but when the Achaeans could not longer hear, he prayed to Apollo. “Apollo, lord of the bow and the lyre, if ever I have pleased you, grant me this wish. Revenge my tears with your arrows.” Apollo heard his prayer and flew down from Olympus, enraged at the insolence of the Achaeans. Plague-filled arrows flew from his bow: first at the mules, then the dogs, then the men he struck again and again. Soon, day and night, tall funeral pyres burned on the beach.