The Prophet's flower

Hussain (PBUH) spent his childhood with Lady Fatimah (PBUH), Imam Ali (PBUH), and especially with Prophet Muhammad (PBUH&HP). The love and affection Prophet Muhammad (PBUH&HP) had towards Hussain (PBUH) was so unique that all the companions were aware of it, had frequently seen its manifestation, and had heard of it repeatedly. Moreover, historians have recorded incidents and narrations in this respect. In one account it has been said that the Prophet's prostration took longer than usual in his prayer. People came to the Prophet and asked, "Were you receiving a revelation or order from Allah during prostration?" Prophet Muhammad (PBUH&HP) replied, "No, my son Hussain had climbed onto my back; I waited until he wished to come down." This is an example showing how the best creature of Allah (SWT) treated Hussain (PBUH) while he was in the best state of worship.  

The companions had seen Prophet Muhammad (PBUH&HP) repeatedly put Hassan and Hussain (PBUT) on his shoulders and play with them. At other times he would kiss Hussain (PBUH) and say, Hussain is from me, and I am from Hussain. May Allah love him who loves Hussain [1] In other traditions the Prophet would say, Hassan and Hussain (PBUT) are my two aromatic flowers from this world [2]

References:

1. al-Tareekh al-Kabeer, al-Bukhari, vol.8, p.414.
2. al-Sahih al-Bukhari, vol.2, p.306.