Or HaChaim on Exodus 23:32/אור החיים על שמות כ״ג:ל״ב

1 לא תכרות להם..ברית, "Do not enter into a covenant with them and their deities." Why does the Torah have to prohibit such covenants since G'd had already commanded the Jewish people (verse 24) to destroy these people? Besides, what would be the purpose of concluding a covenant with the deities rather than the people?

2Actually, we must understand the verse as teaching us that the entire prohibition of concluding treaties with the Gentile nations is applicable only as long as the Gentile nations still adhere to their deities. Once they have denied their former deities this prohibition becomes void. This is why the Torah linked the prohibition by the words להם ולאלוהיהם, "with them and their deities."

3The wording of the prohibition also indicates that G'd views anyone who enters into a covenant with an idol worshiper as if he had made a covenant with idolatry. There are two reasons for this. 1) In the end the Jew will stumble and become guilty of idol worship as a result of obligations he took upon himself; the Torah spells this out in verse 33: "lest they will cause you to sin." 2) The second consideration is that the clothing worn by pagans reflects and symbolises their deities. When making a covenant with such people it appears as if one makes the covenant with their beliefs, G'd forbid. It is not sufficient that one had intended to conclude the deal only with the person and not with his beliefs. If the Torah had been content with that, the wording would have been: לא תכרות להם ברית ולאלוהיהם instead of the word ולאלוהיהם appearing before the word ברית, covenant. The mention of the word "covenant" at the end of the verse confirms our opinion that the prohibition is valid only when the Gentiles still recognise these deities. It is perfectly permissible to conclude a covenant with an atheist, for instance. This is why the covenant with the Gibeonites was perfectly admissible. If the Israelites subsequently felt cheated and had remorse about that covenant this is explained by the Jerusalem Talmud Shevi-it chapter 6. The Gibeonites originally were in a position of rebels against the Israelites and were guilty of death under the directive: "do not allow anyone to survive" (Deut. 20,16).