Sayyiduna Mu'adh bin Anas (may Allah be pleased with him) reports this saying of the Prophet (peace and blessings be upon him): "Whoever comes to a group, it is binding on him to greet them with salam; and whoever rises from a gathering, it is binding on him to greet with salam." Meanwhile, a man stood up while the Prophet (peace and blessings be upon him) was still speaking, and that man did not greet with salam. So the Prophet (peace and blessings be upon him) said: "How quickly he has forgotten!"
Ahmad and Tabarani recorded it. Its chain contains a narrator, Ibn Lahi'ah, and a narrator, Zabban bin Fa'id; both of them have been declared da'if (weak), and the hadith of both has been declared hasan (good).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الأدب / 12757
Hadith Gradingمحدثین:إسنادہ حسن
Hadith Takhrij«اخرجه الطبراني فى المعجم الكبير (186/20) اخرجه احمد فى المسند (438/3) ، أخرجه مسند أحمد برقم: 15188»