Knowing that Apollo can prevent a recurrence of the plague he sent, they purify themselves in a ritual and offer him a large sacrifice of cows, called a hecatomb.
nˈoʊɪŋ ðæt ɐpˈɑːloʊ kæn pɹɪvˈɛnt ɐ ɹᵻkˈɜːɹəns ʌvðə plˈeɪɡ hiː sˈɛnt, ðeɪ pjˈʊɹɹᵻfˌaɪ ðɛmsˈɛlvz ɪn ɐ ɹˈɪtʃuːəl ænd ˈɔfɚ hˌɪm ɐ lˈɑːɹdʒ sˈækɹᵻfˌaɪs ʌv kˈaʊz, kˈɔːld ɐ hˈɛkɐtˌuːm.