But context shows he is talking about his second coming.
I presume by “second coming” you mean Jesus’ coming in glory at the end of the world. I find nothing in the context of Mt. 10:23 that indicates Jesus is talking about His final coming at the end of the world. The context I see is Our Lord’s instruction and counsel to the 12 apostles for their first preaching mission alone - without Jesus along.
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Could you please point out which verse/s in Matthew 10 you think show the context is Jesus instructing/talking the apostles about His final coming at the end of the world.
10:5 These twelve Jesus sent out, charging them, "Go nowhere among the Gentiles, and enter no town of the Samaritans, 10:6 but go rather to the lost sheep of the house of Israel.
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10:16 "Behold, I send you out as sheep in the midst of wolves; so be wise as serpents and innocent as doves.
10:17 Beware of men; for they will deliver you up to councils, and flog you in their synagogues,
10:18 and you will be dragged before governors and kings for my sake, to bear testimony before them and the Gentiles.
10:19 When they deliver you up, do not be anxious how you are to speak or what you are to say; for what you are to say will be given to you in that hour;
10:20 for it is not you who speak, but the Spirit of your Father speaking through you.
10:21 Brother will deliver up brother to death, and the father his child, and children will rise against parents and have them put to death;
10:22 and you will be hated by all for my name’s sake. But he who endures to the end will be saved.
10:23 When they persecute you in one town, flee to the next; for truly, I say to you, you will not have gone through all the towns of Israel, before the Son of man comes.
10:24 "A disciple is not above his teacher, nor a servant above his master; 10:25 it is enough for the disciple to be like his teacher, and the servant like his master. If they have called the master of the house Be-el’zebul, how much more will they malign those of his household.
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11:1 And when Jesus had finished instructing his twelve disciples, he went on from there to teach and preach in their cities.