Is it true that Mu'awiyah exhumed the graves of the Companions and cut off Hamza's finger, and that Abu Sa'id al-Khudri said: "After this, no one will ever deny anything," and is this incident mentioned in the books of Sunnah, specifically in Ibn al-Mubarak's book "Al-Jihad"?

Ibn al-Mubarak narrated a hadith from Jabir ibn Abdullah, in which he mentioned that Mu'awiyah wanted to construct an aqueduct ("al-kadhamah," a water channel). So, he called for anyone whose relative was martyred at Uhud to be present. They brought out the martyrs, fresh and flexible, to the extent that when a pickaxe struck one of their fingers, it bled. Abu Sa'id al-Khudri commented, "After this, nothing will ever be considered reprehensible."

This hadith does not impugn Mu'awiyah, because he did not order the exhumation of graves out of disrespect, but for a public interest, which was to provide water for the Muslims and protect the graves from floods, by moving the buried bodies to a more distant place in the presence of their relatives. Abu Sa'id's statement refers to the martyrs' dignity and the preservation of their bodies as they were buried. This is what Ibn al-Mubarak intended by this hadith in his book on Jihad, to show the virtue of martyrdom.

Al-Baji permitted digging up a grave and exhuming the deceased for a public interest, as long as it did not cause harm, citing as evidence the exhumation of the graves of Abdullah ibn Amr and Amr ibn al-Jamuh due to a flood, and their relocation. Similarly, al-Bukhari titled a chapter "Is it permissible to exhume the deceased from the grave and crypt for a reason?" and narrated the hadith of Jabir, who exhumed his father from the grave after six months and found him as if he had just been placed there, which indicates the permissibility of exhumation for a matter related to the living.