Oneness, Uniqueness of Allah (Tawheed)

Bukhari :: Book 9 :: Volume 93 :: Hadith 572

Narrated 'Abdullah bin 'Umar:

The Prophet besieged the people of Ta'if, but he did not conquer it. He said, "Tomorrow, if Allah will, we will return home. On this the Muslims said, "Then we return without conquering it?" He said, 'Then carry on fighting tomorrow." The next day many of them were injured. The Prophet said, "If Allah will, we will return home tomorrow." It seemed that statement pleased them whereupon Allah's Apostle smiled.