What is the authenticity of this statement narrated from Mujahid concerning the trial of three types of people on the Day of Resurrection (the rich, the sick, the slave), and their comparison to prophets (Solomon, Job, Joseph), and how did Imam Mujahid know what would happen on the Day of Resurrection?

The aforementioned narration has a weak chain of transmission due to the presence of Layth ibn Abi Sulaym, who is unanimously considered weak by scholars. Even if it were authentic, it would not serve as proof for the following reasons:

1. The narration is a statement by Mujahid, and it is classified as "maqtu‘" (قطع — disconnected). The sayings of the Tabi‘in (Successors) are not a proof in religion.

2. Even if it were considered to have the ruling of a Marfu‘ (مرفوع — elevated) Hadith, it would be a Mursal (مرسل — indirectly transmitted) Hadith (a Tabi‘i narrating from the Prophet without mentioning the Companion), and Mursal Hadith is categorized as weak.

3. Mujahid ibn Jabr used to learn from the People of the Book. What he says concerning matters of the unseen is not given the ruling of a Marfu‘ Hadith if he took it from them, due to the possibility that it might be something he received from them.