Abu Salamah relates that Sayyiduna Sa'd bin Mu'adh (may Allah be pleased with him) said: There are three qualities in me: whatever the Messenger of Allah (peace and blessings be upon him) narrated, I affirmed it and knew that it was the truth; I never attended a deceased person but I occupied my heart with reflecting on what it says and what is said to it; and I never offered a prayer in which I let any other thought enter my mind until I completed my prayer.
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 5303