The agent of an infinitive (when it is expressed) will be in the accusative case (GGBB p192; Robertson p489).
καὶ ἀπέστειλεν αὐτοὺς κηρύσσειν τὴν βασιλείαν τοῦ θεοῦ καὶ ἰᾶσθαι τοὺς ἀσθενεῖς (Luke 9:2)
In this verse, αὐτοὺς is the agent of the infinitive κηρύσσειν.
See also §2022.