It is written in “Futuhush Shaam” and other books of history and also in Tafseer Kabeer that Heraclius (ruler of Rome) wrote to Hadhrat Umar Bin Khattab (May Allah be well pleased with him) that I have been suffering from headache for a very long time, which does not abate even for a moment. You please send some medicine for this.
Hadhrat Umar (May Allah be well pleased with him) sent a cap, which when placed on the head would immediately relieve his headache. When it was removed, the headache would come back on again. Heraclius was very surprised with this and he started searching through the cap. He got a paper on which “Bismillahir Rahmannir Raheem” بسم الله الرحمن الرحيم was written (in Arabic script). On this Heraclius said: Sublime is He! What a great name through whose blessings, the Lord granted me cure.
After that, that cap was passed on through his progeny generation after a generation as a blessing, to the 
point that it reached one of the provinces, which later on came under Islamic rule. When Motasim, the caliph, passed through that area, by chance he started suffering from a serious headache. Then this cap was sent to him and as soon as he placed it on his head, his headache abated. He ordered that the cap be stripped and on doing so, the paper with “Bismillahir Rahmannir Raheem” بسم الله الرحمن الرحيم was found.
It is given in Tafseer Kabeer and also books of history that a Zoroastrian came to Hadhrat Khalid Bin Walid (May Allah be well pleased with him) and asked him: Whatever claims you have about Islam and they way you consider your religion to be true, why do believe that your religion is true and if you are true, then show a sign of the trueness of your religion.
On this Hadhrat Khalid Bin Walid (May Allah be well pleased with him) sent for the most potent poison. A box was brought to him, whose smallest piece was also fatal. Hadhrat Khalid (May Allah be well pleased with him) took the whole of it, said “Bismillahir Rahmannir Raheem” بسم الله الرحمن الرحيم and ate everything. By the grace of Allah Ta’ala, nothing happened to him. On this, the Zoroastrian said: Indeed! This religion is true.
It has been narrated that the Pharaoh, before claiming godhood, constructed a house and got the blessed name of Allah Ta’ala inscribed on its door. Then he claimed godhood and Prophet Moosa (Peace be upon him) was sent to guide him. How much ever he (Peace be upon him) would try to guide him, the effect would be the reverse. At last Prophet Moses (Peace be upon him) supplicated: O Lord! I have spared no effort in preaching to him and trying to guide him to the right path. However, no results are to be seen. There are no good hopes with him either. The Lord Almighty said: O Moosa (Peace be upon him)! Maybe that your intention is to kill him? But Moosa (Peace be upon him), you are seeing his apostasy and denial and We are seeing the name on his door.
Thus, there are so many benefits and blessings of “Bismillahir Rahmannir Raheem” بسم الله الرحمن الرحيم that they are inestimable. Hadhrat Sulaiman (Peace be upon him) ruled over the humans and genies through its blessings and through its blessings, the ark of Prophet Noah (Peace be upon him) was saved from capsizing, that when he had removed the anchor of the ship, he had recited “Bismillahir Rahmannir Raheem”.
