Bismillah Arrahman Arraheem
As-salamu alaikum wa Rahmatullahi wa Barakatoh,
Angel Jibra'il (alayhi salām) said to Holy Prophet Muhammad al Mustafā (salla llāhu ʿalayhi wa-alehe wa-sallam):
“...A hundred thousand angels from every sky will descend and surround him (grave of Imām Husain (alayhi salām)) everyday and every night. They will invoke blessings on him, circulate his grave, sanctify Allāh near his grave and seek forgiveness for those who come to his Ziyarat and record the names of those from among your Ummah who seek nearness to the Almighty Allāh and to you, by going to his Ziyarat. They will also record the names of their ancestors, tribes and homelands. Then these angels will mark the faces of the visitor using a marker made of the light of Allāh’s Throne which reads, “This is the Visitor of the grave of the best of the martyrs and son of the best of the prophets.”
Hence on Judgment Day, the light which is from this marking will radiate from their faces in such a way that it will blur everyone’s vision and the visitors will be identified by this light...”
[Reference: Kamiluz Ziyaraat, Chapter 88, page 285]