The paper is an academic study of a diplomatic document revealing relations between the RussianState and the Safawid Persia which now belongs to the RSAAA (Russian State Archive of Ancient Acts) collection and has been overlooked by academic tradition so far. The letter by Shah Safi I to Mikhail Fyodorovich Romanov has never been the focus of scholars for quite a long time; the text of the letter is published in this paper. More so, the document was inaccurately attributed in time when the archive inventory was compiled. The letter was translated to identify the year and the background of its production. The text of the message refers to a famous Russian intellectual A. S. Romanchukov who was staying with Shah Safi I and his court in 1636-1637 together with an embassy from Holstein. This fact and the text of the letter suggest that Romanchukov was a low-rank official in Russian diplomatic mission who delivered Russian tsar's letter of courtesy to Shah Safi I.