Sahih Muslim Book 24, Hadith Number 5293.

Chapter : Prohibition of sitting on the roadsides and to honour the obligations of the roadside.

Abu Sa’id Kbudri reported Allah’s Apostle (may peace be upon him) as saying: Avoid sitting on the paths. They (his Companions) said: Allah’s Messenger, there is no other help to it (but to sit here as we) hold our meetings and discuss matters there. Thereupon Allah’s Messenger (may peace be upon him) said: If you have to sit at all, then fulfil the rights, of the path. They said: What are their rights? Thereupon he said: Keeping the eye downward (so that you may not stare at the women), refraining from doing some harm to the other and exchanging mutual greetings (saying as-Salamu ‘Alaikum to one another) and commanding the good and forbidding the evil.