And do not be afraid of those killing the body but who are unable to kill the soul; but rather fear the one able to destroy both soul and body in gehenna. (Matt. 10:28)
This verse comes in the context of Jesus’ instructions to the twelve before sending them out to proclaim the imminence of the reign of God (10:7). In particular it presupposes the warning that they will face persecution from the Jews as they go through the towns of Israel (Matt. 10:23). There is no thought here of a mission to the Gentiles as such, but as they proclaim the coming of the kingdom of God to Israel, they can expect to be dragged before both Jewish and Roman authorities (10:17-18).
He tells them not to be afraid of their persecutors because although they can kill the body, they cannot destroy the fundamental integrity of a person who carries on the mission of the Son of man. They will be vindicated - by way of resurrection if necessary—at the coming of the Son of man to receive the kingdom. But they should fear—as all Israel should fear at this time of eschatological crisis—the God who will utterly destroy rebellious Israel, without hope of restoration or resurrection to life, in the coming judgment. The image of gehenna is drawn from Jeremiah’s vivid account of the horrors of the Babylonian invasion (Jer. 7:30-33; 19:6-8). Just as the bodies of Jerusalem’s dead were thrown into the Valley of Hinnom when the Babylonians attacked, so Jesus imagines the dead piling up in the valley of gehenna during the war against Rome. What the prophet Jesus imagines the historian Josephus describes:
Now the seditious at first gave orders that the dead should be buried out of the public treasury, as not enduring the stench of their dead bodies. But afterwards, when they could not do that, they had them cast down from the walls into the valleys beneath. (War 5.12.3).
The surprising dualism of ‘body’ and ‘soul’ in this verse appears to reflect specifically a Hellenized martyr theology, rather than general philosophical terminology; for example:
When he was about to die under the blows, he groaned aloud and said: “It is clear to the Lord in his holy knowledge that, though I might have been saved from death, I am enduring terrible sufferings in my body under this beating, but in my soul (psuchēn) I am glad to suffer these things because I fear him.” (2 Macc. 6:30; cf. 7:37)
Each of them and all of them together looking at one another, cheerful and undaunted, said, “Let us with all our hearts consecrate ourselves to God, who gave us our lives (psuchas), and let us use our bodies as a bulwark for the law. 14 Let us not fear him who thinks he is killing us…. (4 Macc. 13:13)