Hazrat Uwais Qarni (rahimahullah) was a famous Taabi’ee who was well known to be the best of Taabi‘een (i.e. those who met the Sahaabah (radhiyallahu ‘anhum), the companions of Rasulullah (sallallahu ‘alaihi wasallam)).
He lived during the era of Rasulullah (sallallahu ‘alaihi wasallam), but because he had to take care of his mother, he could not meet Rasulullah (sallallahu ‘alaihi wasallam). Rasulullah (sallallahu ‘alaihi wasallam) himself mentioned that Hazrat Uwais Qarni (rahimahullah) was the best of Taabi’een. Rasulullah (sallallahu ‘alaihi wasallam) also mentioned that if Hazrat Uwais Qarni (rahimahullah) had to take an oath that something would happen, then Allah Ta‘ala would make sure that it happened, and if anyone had the chance of meeting him, then he should ask him to make du‘aa for his forgiveness
Rasulullah (sallallahu ‘alaihi wasallam) said to Hazrat ‘Umar (radhiyallahu ‘anhu) and Hazrat ‘Ali (radhiyallahu ‘anhu), “Let Uwais make du‘aa for your forgiveness.”
His virtues are very great. He was martyred in the Battle of Siffeen, fighting on the side of Hazrat ‘Ali (radhiyallahu ‘anhu).
When he came to Madinah Munawwarah after Haj, he entered the musjid where someone pointed out to him the resting place of Rasulullah (sallallahu ‘alaihi wasallam). After seeing it, he became so deeply affected that he fell unconscious. After getting up, he said, “Take me out of this city, as I will never find rest in this place where lies buried the most beloved Rasul of Allah (sallallahu ‘alaihi wasallam).”
(Fazaa’il-e-Madinah)