In order to understand why it always says by Balaam that "and Balaam lifted up his proverb and said" (Numbers 23:7 etc.). Furthermore, why did G-d specifically choose to bless the Jews through Balaam? If G-d wanted to bless the Jews, he could have done so through a true prophet. The real meaning of a proverb here is the way that Rashi explains the first verse of the book of Proverbs, being "to understand proverb and analogy", that one's heart should never leave even the analogy. A proverb is something with no source that could be in reality, like the one opinion in the Talmud that the story of Job "never really happened, for it was merely a proverb". This was the difference between the true prophets and the prophecy of the wicked Balaam. The entire prophecy of Balaam was merely a proverb, because it had no root, because he was not really worthy of receiving prophecy, rather it was a proverb, "that never really was", for it had no root in analogy, which is the root on which the prophecy can rest. This is because he was a very unclean person, so he was not actually worthy to receive prophecy, but was merely a proverbial prophet. True prophets had true prophecy. The true prophets were actually worthy to prophecy, therefore they had the analogy, which is the root of prophecy. That is why G-d chose to bless Israel specifically through the wicked Balaam. Because the blessings that come through true prophets come because they are actually worthy to receive the blessings and the drawing down of goodness. Then there had to be potential in the person to be brought into actuality. Then if the Jewish people were vessels that were fit to receive the blessings, then they will receive the outpouring of the blessings. But the wicked Balaam was not truly worthy to bring down the blessings to the Jewish people. He was not a vessel worthy of giving the blessings at all, that he was merely a proverb. Therefore, his blessings can come to the Jewish people even if they are not worthy to receive the blessing, because the entire source of these blessings came without any vessel, because the entire blessing was only on the level of a proverb. That is the meaning of "I have received [an instruction] to bless, and He has blessed, and I cannot retract it." (Numbers 23:20) It means that his blessings can never return empty, even if the Jews are not being good. Despite that "I cannot retract it", no prosecutor can retract the blessing because the blessing came from the wicked Balaam, that is the meaning of "I have received to bless", therefore it comes through this "and He has blessed, and I cannot retract it."
(Divrei Binah - Parshas Balak p. 123)