Shia scholar shaykh Muhammad Rida al-Hukaymi in his book “Sallone an qabla tufqiduni” (1/359) narrated that Ali said to Saad ibn Abu Waqqas:
والله لقد حدثنى خليلى ان على كل طاقة شعر من راسك ملعنك و ان على كل طاقة من لحيتك شيطاناً يغويك و ان فى بيتك سخلاً يقتل ابن راسول الله
By Allah, narrated to me my beloved one that on your head on each hair is an angel, which curse you. And upon each hair of your beard is devil which drives you away (from the truth). In your house there is a kid which would kill the son of prophet (salallahu alaihi wa ali)
Other shia scholar ibn Qawlaveyh in his “Kamil az-Ziyarat” (p 155-156) narrated this with slight difference:
…. and there is no hair on your head or beard except in the root of it is sitting devil, and in your house kid which would kill al-Husayn my son…
Just look at their hate towards this noble companion, hate which forced them to fabricate this lie!
If this narration were true then how is it that Umar ibn Sa’d was allowed to be in the army of the ‘infallible’ Imam Hassan ibn Ali (ra)?