Musharrif -od-Din Musleh Bin Abdullah Sa'di Sherazi, was a famous poet and author of the seventh century of Hijra. He had a restless soul and led major part of his life in travelling. He travelled and lived a long part of his life in Baghdad, Syria, Hejaz and North Africa. After this he returned to his native land with a lot of experience and knowledge gained by the people of other nations. Sa'di utilized that knowledge and experience in producing his great book "Sa'di Nama" known as Boostan" in 655 A.H, which has been written in the form of "Masnawi". By the next year he wrote another book "Gulistan" which comprised prose and poetry. When Sa'di completed this book, he was recognised as a "Teacher of Ethics" in the world of that age. Now he was not only famous among the common people, but also known to the rulers of his surroundings. These rulers became admirer of his knowledge and wisdom. In 663 A.H Abaqa Khan the son of Halakoo Khan, assumed the throne after demise of his father at the place of "Maragha" near "Hamadan". Abaqa Khan in the beginning of his assumption wrote a letter to Sa'di in Sheraz and desired for a peice of advice and guidance. Sa'di in reply wrote a letter and fulfilled his desire. This letter has immense importance and inspite of the fact that so many centuries have passed but the contents of this letter provide guidance to the rulers of the present era. In this article the contents of this letter have been discussed and analysed, which in fact was written to a ruler but identifies good qualities and sound character of an administrator.