Imâm Muslim reports in the introduction to his Sahîh that Yahya b. Sa’îd once said to Al-Qâsim b. ‘Ubaydillâh:

“Abu Muhammad! It feels horrible and grave that you should be asked a question about this religion and not have knowledge about it or a way to get out [and not look like you don’t know].” He replied, “And why is that?” Yahya replied, “Because you are the son of two great Imâms of Guidance, Abu Bakr and ‘Umar.” Al-Qâsim said, “Even more horrible than this – to those who understand what Allah has taught us – is that I should say something without knowledge or report a narration from someone who is not reliable.”

Al-Qâsim b. ‘Ubaydillâh was the great grandson of Abu Bakr Al-Siddîq on his mother’s side and the great grandson of ‘Umar b. Al-Khattâb on his father’s side. His grandfather was Abdullah b. ‘Umar – Allah be please with them all.