(2) باب مَا جَاءَ فِي سَبْعِ أَرَضِينَ
Narrated Abu Bakra:
The Prophet (ﷺ) said. "(The division of time has turned to its original form which was current when Allah created the Heavens and the Earths. The year is of twelve months, out of which four months are sacred: Three are in succession Dhul-Qa' da, Dhul-Hijja and Muharram, and (the fourth is) Rajab of (the tribe of) Mudar which comes between Jumadi-ath-Thaniyah and Sha ban."
Reference: Sahih al-Bukhari 3197
In-book reference: Book 59, Hadith 8
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 4, Book 54, Hadith 419