In one narration the words are: "Indeed, Allah Almighty records his (the believer's) reward and his voluntary deeds even before this month enters, and He records his (the hypocrite's) reward and his wretchedness even before this month enters."
Imam Ahmad and Imam al-Tabarani in al-Mu'jam al-Awsat recorded this narration through Tamim, the freed slave of Ibn Rummanah. I have not found anyone who has given his biography.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصيام / 4780