הלכה על שבת 291:1

Some additional great evils brought about by this despicable trait: It is well known that the sin of the [primal] serpent was brought about by the lashon hara that it spoke against the Holy One Blessed be He, saying [to Eve]: "He [G–d] ate from this tree [the Tree of Knowledge] and created the world," by which Eve was enticed to do likewise (viz. Shabbath 146a): "The serpent was 'intimate' with Eve and injected zuhamah ['pollution'] into her" — hence, [(the sin of) illicit relations], and also death to all mankind — hence, the spilling of blood. And through this [i.e., lashon hara] it induced Adam and Eve to transgress the will of the Holy One Blessed be He. It follows that one who speaks lashon hara adopts its [the serpent's] trait, which undermines the creation.