Kitab Al-Nawadir (uncommon reports)

And through the same chain of narrators from Aban bin Taghlib that he said: Abu Abdillah عليه السلام said: “When the Qaim عليه السلام reappears, there will be a sign for every person by which he would recognize whether he is righteous or evil-doer. And in it is the sign for those who possess reason and it is the right path.”