Sayyiduna Ibn Abbas (may Allah be pleased with him), concerning the saying of Allah, "The postponing (of a sacred month) is only an increase in disbelief" [Surah al-Tawbah: 37], said: Junadah bin Awf bin Umayyah al-Kinani used to come in the Hajj season every year, and his kunyah was Abu Thumamah. He would announce: Abu Thumamah is neither loved nor faulted. Behold! He would declare the month of Safar lawful for the people one year and sacred another year, and he would count the month of Muharram as sacred one year. Allah says: "The postponing (of a sacred month) is only an increase in disbelief, by which those who disbelieve are led astray; they make it lawful one year (and forbid it another year)" up to His saying, "(Allah) does not guide the disbelieving people" [Surah al-Tawbah: 37].
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9774