On the prohibition against fasting before Ramadan after the middle of Sha'ban

Riyad as-Salihin (The Meadows of the Righteous)

by Imam Nawawi

219. Chapter: On the prohibition against fasting before Ramadan after the middle of Sha'ban unless that fasting is connected to what is before it and coincides with his habit, like fasting Monday and Thursday

1224. Abu Hurayra reported that the Prophet, may Allah bless him and grant him peace, said, "None of you should fast a day or two before Ramadan except for a man who customarily fasts. He should fast that day." [Agreed upon]

1225. Ibn 'Abbas reported that the Messenger of Allah, may Allah bless him and grant him peace, said, "Do not fast immediately before Ramadan. Fast when you see the new moon and break it when you see it. If cloud obscures it, then complete the thirty days." [at-Tirmidhi]

1226. Abu reported that the Messenger of Allah, may Allah bless him and grant him peace, said, "When half of Sha'ban remains, then do not fast." [at-Tirmidhi]

1227. Abu'l-Yaqatan 'Ammar ibn Yasir said, "Anyone who fasts the day which is doubtful has rebelled against Abu'l-Qasim." [Abu Dawud and at-Tirmidhi]