Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: A man came and said: I recited the whole of the Mufassal in one rak'ah. He said: That is rattling through it hastily like poetry. Recite as the Messenger of Allah (peace and blessings be upon him) used to recite: two surahs of the Mufassal in one rak'ah.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9821