Mukhtasar Muslim

Abu Ishaq says: I saw a man who asked Aswad bin Yazid, and he used to teach the Qur'an in the mosque, "Do you recite (muddakkir) with a dal or a dhal?" He replied, "I heard Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with them both) saying, 'I heard the Messenger of Allah (peace and blessings be upon him) reciting (fahal min muddakkir) with a dal.'" (That is, the letter without a dot.)