Jami` at-Tirmidhi 2485

Abdullah bin Salam said:"When the Messenger of Allah (s.a.w) arrived- meaning in Al-Madinah – the people came out to meet him. It was said that the Messenger of Allah (s.a.w) had arrived, so I went among the people to get a look at him. When I gazed upon the face of the Messenger of Allah (s.a.w), I knew that this face was not the face of a liar. The first thing that he spoke about was that he said: 'O you people! Spread the Salam, feed(others), and perform Salat while the people are sleeping; you will enter Paradise with(the greeting of) Salam.'” (Sahih)