Ibn Saʿd said: His mother was an umm walad—a concubine who had borne her master a child—by the name of Sawdah. He himself was reliable, learned, of high standing, a jurist, an imam, scrupulously pious, and prolific in ḥadith.

Mūsā ibn ʿUqbah, on the authority of Muḥammad ibn Khālid ibn al-Zubayr, related:
“I was with ʿAbd Allāh ibn al-Zubayr when al-Qāsim ibn Muḥammad requested permission to enter. Ibn al-Zubayr said, ‘Let him in.’ When he came in, he asked him, ‘Mahyam(1)?’ He replied, ‘So-and-so has died…,’ and he recounted the story. When he turned to leave, Ibn al-Zubayr looked after him and said, ‘I have never seen any child of Abū Bakr who resembles him more than this young man.’

Al-Qāsim himself said:
“ʿĀʾishah took it upon herself to issue legal verdicts during the caliphates of Abū Bakr and ʿUmar, and she continued to do so until she died. I kept her constant company—despite my youthful frivolities(2)—and I would sit with ‘the ocean,’ Ibn ʿAbbās. I also sat with Abū Hurayrah and Ibn ʿUmar, and I learned in abundance. With Ibn ʿUmar there was exemplary piety, a vast store of knowledge, and a refusal to speak on matters of which he had no knowledge.”

Ibn Shawdhub, on the authority of Yaḥyā ibn Saʿīd, said: “Among all those we met in Madinah, we preferred no one over al-Qāsim.”

Wuhayb, on the authority of Ayyūb—mentioning al-Qāsim—said: “I have never seen a man better than he. Yet he left behind one hundred thousand, and every dirham of it was lawfully earned.”

Al-Bukhārī recorded: ʿAlī narrated to us; Sufyān narrated to us; ʿAbd al-Raḥmān ibn al-Qāsim—who was the finest man of his era—narrated that he heard his father—who was likewise the finest man of his era—say: “I heard ʿĀʾishah say, ‘I perfumed the Messenger of Allah, peace and blessings be upon him…,’” and he went on to relate the rest of the ḥadith(3).