What is the authenticity of the narration reported from Saeed ibn Jubayr regarding his asking Ibn Abbas about the interpretation of Allah's saying: "And We tested you with a severe testing"?

An-Nasa'i and others narrated from Sa'id ibn Jubayr that he asked Ibn Abbas about the interpretation of (وَفَتَنَّاكَ فُتُونًا - And We tested you with a severe test). Ibn Abbas recounted a long story whose summary is that Pharaoh and his courtiers feared the fulfillment of Allah's promise to Ibrahim that there would be prophets and kings among his descendants. So they ordered the killing of every male born to the Children of Israel. Then they agreed to kill males one year and spare them the next. In the year they spared males, Moses' mother conceived Aaron, and in the year they killed, she conceived Moses, which caused her anxiety and sorrow. This is part of the "fitun" (trials).

Al-Haythami and Al-Busiri authenticated the chain of narration of this hadith. Ibn Kathir mentioned that Ibn Abbas received this story from the Isra'iliyyat (Judeo-Christian traditions), from Ka'b al-Ahbar or others, and that the مرفوع (Prophetically attributed) part of it is small and that it contains something objectionable (نكارة).