It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him), he says: The Noble Prophet (peace and blessings be upon him) taught me to recite: {وَلَقَدْیَسَّرْنَاالْقُرْآنَلِلذِّکْرِفَہَلْمِنْمُدَّکِرٍ} A man asked: O Abu Abdur Rahman! Is it "muddakkir" or "mudhakkir"? He replied, The Noble Prophet (peace and blessings be upon him) taught me "muddakkir".