The certainty. Jesus' charge is extraordinarily realistic. Speaking as the Shepherd, he says: "I am sending you out like sheep among wolves" (v. 16a). Arrests, punishments, trials, betrayals by the members of one's own family, and the hostility of people in general, are sure to come (vv. 17-22). Considering the opposition to Jesus, how could missionaries expect otherwise (vv. 24-25; cf. Jn 15:20)?
The charge. "Therefore be as shrewd as snakes and as innocent as doves" (v. 16b). As the "innocent," the disciples are emissaries of peace (as was the dove after the Flood), not fomenters of strife. But this quality must be combined with shrewdness. Those are real wolves, not sheep in wolves' clothing. Thus "be on your guard" (v. 17; cf. 1 Pt 5:8). Without shrewdness, innocence becomes naïvete. The term behind "shrewd" (phronimoi) is used of the serpent in Gen 3:1 LXX. But the disciples' shrewdness is not sinful, for (unlike Satan's) it is under Jesus' authority and combined with innocence.
Witness
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The certainty. Far from impeding the witness, persecution will promote it. "On my account you will be brought before governors and kings as witnesses to them and to the Gentiles" (v. 18). Corresponding to the reference to Jews in v. 17, v. 18 refers to Gentile rulers and their subjects. The datives of v. 18b are to be taken in bonam partem, of a witness aimed at winning the faith of those who hear - as a captive audience, so to speak!
The charge. The disciples are to be "on their guard" against men. But this is no excuse for avoiding their responsibility as missionaries of Christ. What they are to say or how may be in doubt (v. 19); but that they are to witness is understood (cf. v. 27). As for what or how to speak, the Spirit of God may be trusted to supply what is needed (vv. 19b-20); such a supply is an "emergency ration," not a "staple diet" (Leon Morris).
Salvation
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The certainty. The "Lord of the harvest" will not abandon his apostles (28:20). The promise of the Spirit (v. 19) expresses the same reality. V. 40 points to Christ's presence with his representatives. As the One who is to be present with them, Jesus assures them of their salvation: "He who stands firm to the end will be saved" (v. 22b). The best clue for interpreting the much debated v. 23, comes from the statement which immediately precedes it (as just quoted). I.e., the "coming of the Son of Man" (v. 23b) achieves the salvation of his missionaries. I believe Jesus refers here to his Parousia, his second coming, by which event he accomplishes the final deliverance of his people. (Note that v. 22 speaks of him who endures "to the end.") On this showing, the mission to Israel will still be in progress when he returns; this shows in turn that the Church will not have been eradicated (cf. 16:18). Otherwise v. 23 might be interpreted of the coming of the Son of Man in judgment upon the Jewish nation in the war with Rome and the destruction of Jerusalem (A.D. 66-70), amid which events the Jewish Christians fled from the capital.
The charge. Given the promise of salvation, Jesus urges his followers to endure to the end (v. 22, where hypomeno underlies "stands firm"). V. 23 urges them to witness with innocence and shrewdness. Naive innocence might call for staying in one place, whatever the persecution; but shrewdness would call for "fleeing to another." In this way, one runs less risk of the witness being halted (through arrest, trial and death), and also extends the witness to other cities (cf. Acts 8:1 et seq.). Readiness for flight rests on the certainty that one will not have used up places of refuge prior to the final deliverance in the Parousia of the Son of Man. Moreover, while the promise of protection (10:28-30) appears to be chiefly intended to offer hope of final salvation to those who suffer death for their witness (see v. 28a), the passage seems also to include the idea that God will allow nothing to impede the progress of the apostles' witness, and will safeguard them till their particular work is done.
Judgment.
The certainty. The theme of God's judgment is presented in face of men's judgments against Jesus's ambassadors. It is God's judgment about which people ought to be chiefly concerned (v. 28). The process of his judgment begins with the first coming of Jesus (the supremely critical event; the Greek for "judgment" is krisis). Human beings are divided according to their responses to him - which division inevitably causes conflicts between the two companies of people (10:34-38). The language of 10:37 ("loves his father or mother more than me") bears the same meaning as, but is less severe than (and thus a little less arresting than), the parallel in Lk 14:26 ("does not hate his father and mother"). Whether one stands or falls in the judgment depends on whether he has "acknowledged" Jesus before men or has instead "denied" him (10:32-33). The "whoever" (hostis) of 10:32-33 makes the statement comprehensive - to embrace both the bearers and the hearers of the message. The statement includes both disciples (both genuine and phony) and the crowds. The hostis "puts emphasis on the actions of confessing and denying Jesus rather than on the identity of those who perform these actions" (Gundry, 198).
The charge. The twin charge is to fear God (as he is described in v. 28) and to be faithful in fulfilling the commission (cf. B.). Even - or especially - the preacher must keep ever before him the solemn words of 10;32-33, which by their comprehensiveness embrace him.
Reward.
The certainty. Jesus concludes the discourse (10:40-42) by speaking of rewards for the faithful and the believing. He who responds affirmatively to the messengers of Christ - whether they are apostles, v. 40, prophets, v. 41, or mere disciples, v. 42 (cf. Gundry, 203) - will surely be rewarded (note the strong negation, ou mae, of v. 42). (NB that in v. 42 the cup of cold water is given to Christ's messenger, a fact to be remembered when we come to 25:31-46.) The reward is nothing less than the gift of eternal life, the life of the kingdom, the life that is life indeed (v. 39) - the life already promised to the bearers of the gospel (v. 41).
The charge. Only the one who willingly "takes up his cross" to follow Jesus (v. 38), is "worthy" of him (vv. 32-33). Thus "taking up one's cross" means a willingness to go the full distance in demonstrating loyalty to Jesus - i.e. a willingness to die for him (cf. the preceding vv. of the ch.), as Peter and Paul (to name but two) were to do. But more fundamentally v. 38 speaks of a willingness to lose one's life (NB v. 39, immediately following), in the sense of abandoning oneself utterly to Christ's Lordship, and with him (God's Suffering Servant) to take the path of lowliness (one like the road to crucifixion), one which excludes pride, and from which position one is able to follow Jesus' example and fulfill the task of the slave and servant (cf. 20:26-28; Phil 2:1-11). Jesus speaks chiefly of a living sacrifice; cf. Lk 9:23, "take up his cross daily"; also Rom 12:1-2.