Imam Al Hussain (AS) never overtook Al-Hassan (As) when walking with him. This was because of the respect that the younger brother had towards his older one although Imam Al-Hasan was not very much older than his younger brother Imam Al-Hussain. Even when Imam Al-Hassan was talking, Imam Al-Hussain kept silent because of the respect that he had for his older brother and his Imam. This is the true manifestation of politeness and favor.
Once prophet Muhammad was giving a sermon in the mosque when a blind man entered the mosque and without knowing that the prophet is talking asked him to give some pieces of advice. A person who was sitting close to the prophet of Allah got upset and turned his face away from the blind man because of his disrespect towards the prophet. Now, the old man couldn’t see even his anger of turning his look away from himself. This was the time when a Surah with ten Ayahs was revealed to Prophet Muhammad condemning this action of the angry man. This Surah is called Abas عبس starting with the Ayah: "He frowned and turned away".