In the house of the Messenger there was a permanent sense of awe. Those who caught a glimpse of him could feel the allure of Heaven and the terror of Hell. He swayed to and fro during prayer, trembling with the fear of Hell and flying on wings of the desire of Heaven. All who saw him remembered God. Imam al-Nasa'i narrates: "While the Messenger was praying, a sound, like a boiling pot, was heard."  He always prayed with a burning and weeping heart. 'A'isha often found him in the presence of his Master, prostrating and trembling. 
His behavior inspired and benefited everyone around him. The children and wives of every Messenger had the same awe and fear, as the Messengers preached, ordered, related what they practiced and experienced, and gave examples through their actions. We can assess a person's impact through his or her behavior while at home. If all pedagogues gathered and merged their acquired knowledge about education, they could not be as effective as a Prophet.
Many of his descendants have shone among their respective generations like a sun, a moon, or a star. He brought up his Companions so perfectly that almost none of them became heretics.  None of his progeny has ever become a heretic, which is a distinction unique to him. Heretics and apostates have appeared among the households and descendants of many saintly people, but none of Muhammad's descendants have betrayed the roots of their household. If there have been a few exceptions unknown to us and history, they do not negate the rule. 
 Nasa'i, "Ishrat al-Nisa'," 4.
 Very few among the Companions; the apostates after his death are not Companions.)
 There's a rule in logic: Exceptions do not invalidate the rule. We do not know of any heretics among his descendants. But this does not mean that there will not be, because it is possible. Considering this possibility, we speak with caution.)