It is narrated from Sayyidah Aishah (may Allah be pleased with her) that, of all the months, the most beloved month to the Messenger of Allah (peace and blessings be upon him) for fasting was Sha'ban; then he (peace and blessings be upon him) would join it to Ramadan. This hadith is sahih (authentic) on the condition of the two Shaykhs (Bukhari and Muslim), but they did not record it.