It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that when the Messenger of Allah (peace and blessings be upon him) attended a funeral, signs of sorrow could be seen upon him, and he (peace and blessings be upon him) would talk much to himself.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11143