What is the authenticity of the narration regarding Gabriel's descent to the Prophet, peace and blessings be upon him, at the Battle of Mu'tah, and his informing him that ten jewels would be lifted from the earth after his death?

This hadith has no basis or chain of narration in the books of Sunnah or in books of fabricated hadith. It is not permissible to narrate it except to warn against it. It contains blatant discrepancies in its text: The Prophet, may Allah bless him and grant him peace, did not go out to Mu'tah, and Jibreel does not descend to elevate morals. The first things to be lifted from people are khushu' (devotion) and amanah (trustworthiness), not barakah (blessing). And the statement: "I will lift asceticism and piety from scholars" is contradictory, because a true scholar is characterized by asceticism and piety. There is also obvious awkwardness in its expression.