Shaikh Muhammad Rebhâmî, one of the renowned Islamic scholars, relates in the fifteenth page of his book entitled Riyâdun-nâsikhîn, borrowing from the book entitled Zâd-ul-muqwîn:
The Byzantine Kaiser sent an envoy to Me’mûn bin Hârûn, the seventh Abbasid Khalîfa. An awesome and arrogant man was with the envoy. The envoy said to the Khalîfa, “This man is an irreligious unbeliever. He does not believe in a creator. Byzantine priests failed to answer him. If the Islamic scholars manage to silence him, they will make millions of Christians and Muslims happy.”
The scholars of Baghdâd said that there was only one scholar to answer that man, and he was Ahmad Nishâpûrî. The Khalîfa decided on a certain hour of a certain day and ordered all the scholars to convene at the palace. Nishâpûrî was rather late for the session, so he offered the following apology: “I saw something astonishing and quite unusual on my way. Watching it made me late. As I was waiting for the ship at the shore of the Tigris River, a huge tree came out of the earth. Then it fell down and broke into pieces, which presently turned into planks of wood. Then the planks came together to make a ship. Without a captain the ship began to sail.”
When the Byzantine unbeliever heard these words he sprang to his feet and said, “This man must be crazy. Are those things ever possible? He who says so is a liar. One must be without a brain to believe him.” Nishâpûrî interrupted him and said, “When these things cannot take place on their own, how can so many astonishing things on the earth come into being on their own? Mustn’t a person be even more idiotic and more lowly to deny the creator of all these things?”
There upon the unbeliever said, “Now I realize and believe that the entire existence has a creator.” Expressing the statement LÂ ILÂHA IL-L-ALLAH, he became a Muslim. It is narrated that a similar event took place during the time of Imâm Ghazâlî. Khalîfa Me’mûn passed away in the hijrî year 218.
Ref: This paragraphes are quoted from the book “Endless Bliss” first fascicle page 297, which is the translation of the book “Tam İlmihal Seâdet-i Ebediye” written by Hüseyn Hilmi Işık ‘rahimahullâhu ta’âlâ,’ who passed away in 1422 A.H (2011 A.D.) in Istanbul / Turkey. “Tam İlmihal Seâdet-i Ebediye” and “Endless Bliss” published by Hakikat Kitabevi, Istanbul. You can find the whole book and the other valuable books in the web site www.hakikatkitabevi.com.tr and download in PDF format for Adobe Acrobat Reader, EPUB format for iPhone-iPad-Mac devices and MOBI format for Amazon Kindle device.