Jizya
It was the ijtihad of the companions. The process of Itmam e Hujjat extended to the contemporary Persians, too. They ould have been counted as polytheists in that case they would have been killed or as the people of book, in that case Jizya would have been applied to them. The companion due to their holy book from which they adopted their beliefs considered them like the people of book.