“Anyone who associates the aim for the Creator with another thing is uprooted from the world, as was said, ‘to the Lord alone’” (Sukkah 45).
We should understand what it means that one associates another thing. Why is he uprooted from the world? He is committing idol-worship, meaning serves the Creator, as well as that other thing, so his sentence should have been the same as that of an idol-worshipper, so why specifically he is uprooted from the world?
We should interpret that the words “to the Lord alone” do not mean that he is also committing idol-worship. Rather, it means that since one must observe Torah and Mitzvot [commandments] because of the fear of heaven and not for his own delight, when he works for the Creator and also wants to benefit from his work, meaning for his own delight, as well, this is called “associating the aim for the Creator with another thing,” namely himself.
Our sages said about him that he is uprooted from the world because man was created in the world for the purpose of fear of heaven, as our sages said, “The whole world was created only for this, to command this” (Berachot 6b). Thus, one who associates his own delight, as well, is uprooted from the world because his intention is not solely for the Creator. This is the meaning of the verse, “to the Lord alone,” and not for his own delight, as well.