Allah the Almighty says in The Holy Quran:
"By the grace of Allah, you are gentle towards the people; if you had been stern and harsh-hearted, they would have dispersed from round about you." The noble Qur'an, A'al-Umran(3):159
The following is a Hadith from the books of Bukhari and Muslim:
Hadrat Anas ibn Malik (may Allah be pleased with him) said: While we were in the mosque with Allah's Messenger (may Allah's blessings and peace be upon him) a desert Arab came and began to pass water in the mosque. The companions of Allah's Messenger said, "Stop! Stop!" but Allah's Messenger (may Allah's blessings and peace be upon him) said, "Don't interrupt him; leave him alone." They left him alone, and when he had finished, Allah's Messenger (may Allah's blessings and peace be upon him) called him and said to him, "These mosques are not suitable places for urine and filth, but are only for remembrance of Allah, prayer and recitation of the Qur'an," or however Allah's Messenger expressed it.* Hadrat Ibne Malik (may Allah be pleased with him) said that he then gave orders to one of the people who brought a bucket and poured water over it. (Bukhari and Muslim)
*Indicating that the transmitter is not sure of the exact words.