The Messenger of Allah ﷺ said, "When half of Shaban has passed, do not fast."
حدثنا قتيبة حدثنا عبد العزيز بن محمد عن العلاء بن عبد الرحمن عن أبيه
قال رسول الله ﷺ إذا بقي نصف من شعبان فلا تصوموا
No references are available.
Its isnad is sahih. Abu Dawud narrated it in the Book of Fasting, chapter on the dislike of doing that, hadith no. 2337, from Qutayba and so on with the same wording, and Ibn Hibban graded it sahih (Al-Ihsan): 3583. Hadith, "Do not anticipate the month of Ramadan." Previously mentioned: 685, 687.