Muhammad said:
"Don’t ever underestimate any kind act, even if you meet others with a bright (smiling) face." And he said: “The one who greets others first is closer to God than the others.”
On another occasion he said to someone who asked him about a good way to deal with people: “Offer people food and greet whom you know and whom you don’t know."
According to authentic narrations, Muhammad used to meet people with a bright face and when he shook hands with others, he never released his hand before the other person.