12-65 Muhammad ibn Ali Majiluyih - may God be pleased with him - narrated that Ali ibn Ibrahim ibn Hashim quoted his father, on the authority of Muhammad ibn Abi Umayr who linked it up through a chain of narrators to Aba Abdullah as-Sadiq (MGB) who said

the following regarding the Honorable the Exalted God’s words, ‘The number of months in the sight of Allah is twelve (in a year)- so ordained by Him the day He created the heavens and the Earth;…’ They are Muharram; Safar; Rabial-Awwal; Rabial-Akhar, Jamadiul-Awwal; Jamadiul-Akhar; Rajab; Shaban; Ramazan; Shawwal; Dhul-Qa’ade and Dhul-Hijja. Four of them are the sacred months including twenty days in Dhul-Hijja, all of Muharram, Safar and Rabial-Awwal, and the last ten days of Rabial-Akhar.”