Al-Majishun relates that Sayyiduna Sa'd bin Mu'adh (may Allah be pleased with him) said: Except in three things, I am weak (in every matter): I never heard anything from the Messenger of Allah (peace and blessings be upon him) but I was certain that it was the truth; I never offered a prayer in which I let any other thought enter my mind until I finished it; and I never followed a funeral while letting any thought enter my mind other than what the deceased says and what is said to it.
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 5302