‘And he said, “Truly I say to you, no prophet is acceptable in his own country.”'
Then Jesus explained quite firmly (‘truly') why He had performed so few healings in Nazareth (Mark 6:5). It was because no prophet was acceptable in his own area, and especially in his own home town. Thus they did not have the faith even to bring their sick to Him. (Their view was probably that if He was a genuine healer, which they doubted, He ought to seek the sick out for Himself. After all it was His home town. He would know where they were. But although Jesus healed all who came to Him He never sought out the sick. He saw His ministry as one of preaching and proclaiming the Kingly Rule of God. He healed the sick out of compassion).
Note here His repetition of the fact that He is a Prophet. Although they may see Him as only a local boy, and a carpenter, they needed to face up to the fact that He was from God. He then seeks to illustrate His point about unacceptability of prophets in their own country from the Scriptures.
‘Truly I say to you.' (Literally ‘Amen, I say to you'). As used to introduce an authoritative statement in this way this is typical of Jesus' speech and unique (Amen is used elsewhere by others, but only as added to confirm a statement). Although it occurs in Luke only six times (he sometimes translates with ‘nai' or ‘alethos'), it occurs much more often in the other Gospels which show that Luke has amended it. This is partly because Luke regularly smoothes out Aramaisms. Thus when he does leave it in it increases its emphasis (here and in Luke 12:37; Luke 18:17; Luke 18:29; Luke 21:32; Luke 23:43).
Luke gives the proverb in such a way that ‘country' could refer to Israel as a whole, so that it could be read that way by his Gentile readers, so as to make what follows more applicable to them, but here it certainly means his own neighbourhood. There are no Jewish parallels for this proverb, although there is one which says, ‘heal your own lameness', but something like it is found in Gentile writings (our scanty sources for Jewish teaching in 1st century AD are, however very limited). It is, however, the kind of proverb that is very applicable and would quickly spread.