Why did Abu Hurairah narrate a Hadith such as, "Allah created the dust on Saturday...," from Ka'b al-Ahbar, who is known for narrating Isra'iliyat (Judeo-Christian traditions), while all Hadiths in Sahih Muslim are supposed to be authentic?

The aforementioned Hadith was narrated by Muslim, and some scholars have declared it to be flawed, stating that it is from the words of Ka'b al-Ahbar. Ka'b al-Ahbar was a trustworthy Tabi'i (successor), a Jewish scholar who later embraced Islam, and he had knowledge of the books of the Children of Israel. Scholars have agreed upon the authenticity of the Ahadith in Bukhari and Muslim, with rare exceptions. The Prophet, peace and blessings be upon him, permitted narrating from the Children of Israel. However, the Companions did not accept everything Ka'b narrated; rather, they rejected from him whatever contradicted the truth. Mu'awiyah said about him: "And indeed, despite that, we would test him for falsehood."