Sayyiduna Sahl bin Sa'd (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "After me, people will console one another as condolence over me." The people used to say: What is this? Then, when the Messenger of Allah (peace and blessings be upon him) passed away, the people would meet one another and console one another over the death of the Messenger of Allah (peace and blessings be upon him).
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 5736