For unto us was the gospel preached, as well as unto them: but the word preached did not profit them, not being mixed with faith in them that heard it.Paul reminds his audience that the gospel was preached to "us" and "them". A quick look at wikipedia's description of who the audience of this epistle is, doesn't clarify anything; saying that traditionally it has been assumed that the audience is Christian Jews, but it has been pointed out that if the audience is Christian Jews, why was it written in Greek and not Aramaic? - A very good question, at any rate, the content of this epistle is written with certain assumptions that the readers are familiar with Jewish law and custom, and so the traditional assumptions about the audience make sense - regardless of which language it was written in.
Anyway, the point Paul makes here is that when the gospel was preached to "us", it was "mixed" with faith, but when it was preached to "them" it was not. I presume here that both "us" and "them" are "Christian Jews" and "non-Christian Jews". And we must remember that much of the preaching done to the Jews was by Christ himself who said: I am not sent but unto the lost sheep of the house of Israel. (Matthew 15:24)
The difference between the two parties had nothing necessarily to do with the teacher, but the faith or lack thereof of the hearers. I have to ask myself, what caused some to have faith in His message, and some not to? I don't think the answer is simple. Perhaps all who heard Him teach were pricked in the heart, and yet some ignored it. I truly believe one cannot hear truth and not feel it in their soul. However, as in the parable of the sower, some were not prepared to accept it. The situation is described succinctly by the Lord who explains a quote from Isaiah:
For whosoever hath, to him shall be given, and he shall have more abundance: but whosoever hath not, from him shall be taken away even that he hath. Therefore speak I to them in parables: because they seeing see not; and hearing they hear not, neither do they understand. And in them is fulfilled the prophecy of Esaias, which saith, By hearing ye shall hear, and shall not understand; and seeing ye shall see, and shall not perceive: For this people’s heart is waxed gross, and their ears are dull of hearing, and their eyes they have closed; lest at any time they should see with their eyes, and hear with their ears, and should understand with their heart, and should be converted, and I should heal them.So the Lord actually protected those of little faith by teaching parables. So that to those of faith the meaning was apparent, while to those of faith the meaning remained hidden. In many cases, had the lessons been taught in a simple and direct manner the hearers would have understood and been held the more accountable for their disobedience.
I have found that because the parables and other teachings are ofttimes couched in language that is not easily understood, it takes more effort and soul-searching to understand their meaning. But in this way, the understanding is "earned" and therefore more precious to the discoverer. At least, that is the way it is with me.
So the way to make sure we are in the "us" group and not the "them" group is to have faith - pay close attention to that still small voice and trust it. If we do so great treasures of knowledge will be opened to our view.