Q.18:86
Until, when he reached the setting of the sun, he found it set in a spring of murky water: Near it he found a People: We said: "O Zul-qarnain! (thou hast authority,) either to punish them, or to treat them with kindness."
89
Then followed he (another) way,
90
Until, when he came to the rising of the sun, he found it rising on a people for whom We had provided no covering protection against the sun.

Obviously Sun rises and sets in ALL places, or actually no place at all. One doesn’t have to go "another way" to find it rising. This gives us the clue that Muhammad really believed that the Earth is flat and the sun moves in the sky rising from one place, setting in another. 

But how can we be sure this is how Muham-mad thought of the shape of the Earth? The answer can be found in another Hadith. 


Sahih Bukhari Volume 4, Book 54, Number 421Narrated Abu Dhar:
The Prophet asked me at sunset, "Do you know where the sun goes (at the time of sunset)?" I replied, "Allah and His Apostle know better." He said, "It goes (i.e. travels) till it prostrates Itself underneath the Throne and takes the permission to rise again, and it is permitted and then (a time will come when) it will be about to prostrate itself but its prostration will not be accepted, and it will ask permission to go on its course but it will not be permitted, but it will be ordered to return whence it has come and so it will rise in the west. And that is the interpretation of the Statement of Allah: "And the sun Runs its fixed course For a term (decreed). that is The Decree of (Allah) The Exalted in Might, The All-Knowing." (Q. 6: 3 

Ok. Here we have a case in Hadith that is confirmed by the Quran, which is again ratified by another Hadith and once more demonstrated in the Quran. Is this Hadith against the science and commonsense? It sure is. However. it is not against the Quran. Therefore the message conveyed by the Hadith is wrong, despite the fact that it is an authenticated Hadith. 
If we have any doubts about what Muham-mad really thought of the shape of the Earth, we can safely put them to rest when we read the following verses. 

Q. 78: 6
Have We not made the earth as a wide expanse,
7
And the mountains as pegs?

The “expanse” gives an idea of something flat. The Arabic word used in the Quran is Mehad, (bed). All the beds that I have seen so far were flat. None of them where spherical. Also the mountains are not pegs keeping the earth from shaking as the prophet used to think.

Don’t these Hadithes, backed by these verses from the Quran, clearly describe a flat Earth, with the Sun rising from one end and setting in the muddy waters on the opposite end? Is there a Throne somewhere that the Sun goes under it to get permission? What Throne was Muhammad talking about? When and how the Sun prostrates itself? This concept sounds ridiculous to us; yet in the old ages everyone believed in a flat Earth, floating on waters surrounded by high mountains beyond which one could fall into an abyss, etc. and the whole story made perfect sense to those who heard it. 

Naam, huyu ndie Marehemu Mtume Muham-mad, amejaa vioja kama nini. Tatizo ni kale kaugonjwa ka akili alikokuwa nako, na tumajini aliyokuwa ametupiwa.

Burudika na vioja vya Muhammad.