The Prophet ﷺ forbade fasting in Rajab.
حدثنا إبراهيم بن المنذر الحزامي حدثنا داود بن عطاء حدثني زيد بن عبد الحميد بن عبد الرحمن بن زيد بن الخطاب عن سليمان عن أبيه
أن النبي ﷺ نهى عن صيام رجب
No references are available.
[Its chain is daif] Tabarani narrated it in al-Kabir, 10/348, no. 10681, from the hadith of Ibrahim bin Munzir, via this route.Dawud bin Ataa is daif (Taqrib), and there is consensus on his being weak (marginal note of Sindi). Ibn Jawzi and Dhahabi both declared the hadith daif.