(Go you with this letter of mine and deliver it to them then draw back from them and see what they return.) Sulayman wrote a letter to Bilqis and her people and gave it to the hoopoe to deliver. It was said that he carried it on his wings, as is the way with birds, or that he carried it in his beak. He went to their land and found the palace of Bilqis, then he went to her private chambers and threw the letter through a small window, then he stepped to one side out of good manners. Bilqis was amazed and confused when she saw that, then she went and picked up the letter, opened its seal and read it. The letter said:
It is from Sulaiman and it is (in the following words:) With the name of Allah, the All-Merciful, the Very-Merciful. 27:30
There is not a single aspect of human life on which Qur'an does not provide guidance. Mutual exchange of welfare and other information through letters is part of human requirements. In this Surah, full text of the letter from Sayyidna Sulaiman (علیہ السلام) to Queen Saba' has been reproduced. This is a letter from a prophet, and Qur'an has reproduced it as an approved format for a letter. Hence, it should be taken in that light and Muslims should try to follow the guidance provided in it for letter writing.
The Sabeans were a wealthy community of ancient times (1100 B.C. to 115B.C.). Their country was located in Ma‘arib (Yemen), where its grand ruins are still in existence. During Solomon’s period, this area was under the rule of a queen called Sheba (Bilqis). The people of this place used to worship the sun, Satan having taught them that the only thing worth worshipping was whatever was most prominent. As the sun was the most prominent of all visible things, only the sun, therefore, deserved to be considered a god and worshipped. Solomon received detailed information about the Sabeans through the hoopoe bird. This hoopoe perhaps belonged to Solomon’s army of birds and possibly received regular training.
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.