Sahih Muslim Book 2, Hadith Number 516.

Chapter : Easing is forbidden in the streets and under the shade.

Abu Huraira reported: The Messenger of Allah (may peace be upon him) said: Be on your guard against two things which provoke cursing. They (the companions present there) said: Messenger of Allah, what are those things which provoke cursing? He said: Easing on the thoroughfares or under the shades (where they take shelter and rest).