He used to urge his Companions to fast three days of every month. Observing voluntary fasting during the sacred months or Al-Ashhur Al-Hurum, including the month of Rajab, is recommended. Prophet Muhammad (peace be upon him) instructed his Companions to observe voluntary fasting in these months. Thus, fasting in Rajab is recommended but there is no authentic hadith that indicates that fasting certain days of Rajab, for example the first day, entails a special reward.