Dialects and Readings of the Qur'an (Kitab Al-Huruf Wa Al-Qira'at)
Dawud :: Book 30 : Hadith 3983
Narrated Abdullah ibn Mas'ud:
The Prophet (peace_be_upon_him) used to read the verse "Is there any that will receive admonition (muddakir)? " that is with doubling of consonant [(dal)(d)].