Sayyiduna Abdullah bin Amr bin al-As (may Allah be pleased with them both) said: I heard the Messenger of Allah (peace and blessings be upon him) when we set out from Ta'if; we passed by a grave, and he (peace and blessings be upon him) said: "This is the grave of so-and-so. He used to be protected by this sanctuary. When he left it, the calamity that had struck his people struck him at this very place, and he was buried in it. The sign of this is that his golden rod is buried with him; if you open his grave, you will find it with him." So the people hastened to it and took the rod out from there. And this grave was the grave of Abu Righal.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7652
Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) said that they were with the Messenger of Allah (peace and blessings be upon him) on a journey, and they passed by a grave. He (peace and blessings be upon him) said: "This is the grave of Abu Righal, who was from the people of Thamud. When Allah destroyed his people with what He destroyed them with, he was spared because he was in the Sanctuary. Then he left it, and when he reached this place he died, and he was buried, and his golden rod along with him." So we hastened and took it out from there.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7653
Jarir bin Rabah narrates from his father that they found a grave in al-Mada'in, and in it they found a man wearing clothes woven with gold, and they also found wealth with him. They came to Ammar bin Yasir (may Allah be pleased with him), and he wrote to Umar (may Allah be pleased with him) about it. Umar (may Allah be pleased with him) wrote back to him that he should give it to them and not take it away from them.
The Shaykh said: If they found it in dead (unowned, uncultivated) land, then they own it and there is khums in it; it seems that it did not reach the nisab, or he left that to them so that they would pay it themselves. And Allah knows best.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7654