Bukhari Volume 1, Book 4, Number 145:
Narrated Ibn 'Abbas:
Once the Prophet entered a lavatory and I placed water for his ablution. He asked, "Who placed it?" He was informed accordingly and so he said, "O Allah! Make him (Ibn 'Abbas) a learned scholar in religion (Islam)."
Mohammad praised Ibn Abbas for ensuring that Mohammad had water to clean himself after answering the call of nature. Ibn Abbas' deed was so central to the core of Islam that the prophet (without any prophecies) prayed his follower would be a learned scholar in Islam.
At first blush, this passage does not seem quite impressive at all. However, it is the unimpressive things that tell alot about an ideology.
In this case, Mohammad believed that the path to understanding Islam was bodily cleanliness as opposed to spiritual cleanliness. Why else would he pray that Ibn Abbas become a learned scholar of Islam when the focus of Ibn Abbas' action were physical as opposed to spiritual?
Second, Bukhari implicitly connects Islam to the toilet. He boldly shows that the true heart of Islam for Mohammad centers on cleaning one's self after they answer the call of nature, as opposed to cleansing the soul after one sins.