For all posts on Balak click here
Rashi says that we don’t want Bilam‘s blessing, as we don’t want the bee’s sting or it’s honey. Rashi asks where the leap is from realizing it would be fruitless to curse them, to actually wanting to bless them. The question makes it difficult to understand the parable; if you don’t get stung, of course you want the honey!
R’ Yosef Shwartz (the Giznei Yosef) explains that the reason behind the fact that Rivka’s family had blessed her, and she became barren. From here its clear that an evil person’s blessings are not fulfilled and in this case, it was, to the degree that the blessing was, in effect, a curse.
This was Bilam‘s intention. He would NOT be miskayem (fulfilling) the blessing, as was the case with Rivka! Clearly this blessing (honey) has the sting in the tail! Therefore, Rashi’s nimshal (explanation of the connection of the story to the matter at hand) is very apt indeed!
The difference is that Rivka’s family blessed her and this is the source that an evil person’s blessing is not mekuyam (fulfilled), to the degree that she became barren. But the Jews were already blessed by Hashem, so Bilam‘s “blessing” couldn’t not be fulfilled as it was after the fact they were chosen and blessed! That’s why it says, “I (God) have blessed them” – so your “blessing” can’t have an effect one way or another!