At-Tawbah 9:36

<h2>The Year consists of Twelve Months</h2><p>Imam Ahmad recorded that Abu Bakrah said that the Prophet said in a speech during his Hajj, </p><div class="arabic uthmani">«أَلَا إِنَّ الزَّمَانَ قَدِ اسْتَدَارَ كَهَيْئَتِهِ يَوْمَ خَلَقَ اللهُ السَّمَوَاتِ وَالْأَرْضَ، السَّنَةُ اثْنَا عَشَرَ شَهْرًا مِنْهَا أَرْبَعُةٌ حُرُمٌ، ثَلَاثَةٌ مُتَوَالِيَاتٌ: ذُو الْقَعْدَةِ وَذُو الْحِجَّةِ وَالْمُحَرَّمُ وَرَجَبُ مُضَرَ الَّذِي بَيْنَ جُمَادَى وَشَعْبَان»</div><p>ثم قال: </p><div class="arabic uthmani">«أَيُّ يَوْمٍ هَذَا»</div><div class="arabic uthmani">قلنا: الله ورسوله أعلم، فسكت حتى ظننا أنه سيسميه بغير اسمه قال: </div><div class="arabic uthmani">«أَلَيْسَ يَوْمَ النَّحْرِ»</div><div class="arabic uthmani">قلنا: بلى ثم قال: </div><div class="arabic uthmani">«أَيُّ شَهْرٍ هَذَا؟»</div><p>قلنا: الله ورسوله أعلم، فسكت حتى ظننا أنه سيسميه بغير اسمه قال: </p><div class="arabic uthmani">«أَلَيْسَ ذَا الحِجَّةِ؟»</div><p>قلنا: بلى، ثم قال: </p><div class="arabic uthmani">«أَيُّ بَلَدٍ هَذَا؟»</div><div class="arabic uthmani">قلنا: الله ورسوله أعلم فسكت حتى ظننا أنه سيسميه بغير اسمه قال:</div><div class="arabic uthmani">«أَلَيْسَتِ الْبَلْدَةَ؟»</div><div class="arabic uthmani">قلنا: بلى»</div><p>(The division of time has turned to its original form which was current when Allah created the heavens and the earth. The year is of twelve months, out of which four months are sacred: Three are in succession Dhul-Qa`dah, Dhul-Hijjah and Muharram, and (the fourth is) Rajab of (the tribe of) Mudar which comes between Jumada (Ath-Thaniyah) and Sha`ban." The Prophet then asked, (What is the day today') We …

Lo! the number of the months with Allah is twelve months by Allah's ordinance in the day that He created the heavens and the earth. Four of them are sacred: that is the right religion. So wrong not yourselves in them. And wage war on all of the idolaters as they are waging war on all of you. And know that Allah is with those who keep their duty (unto Him).

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; of them four are sacred: that is the straight usage. So wrong not yourselves therein, and fight the Pagans all together as they fight you all together. But know that Allah is with those who restrain themselves.

Verily, the number of months with Allah is twelve months (in a year), so was it ordained by Allah on the Day when He created the heavens and the earth; of them four are Sacred, (i.e. the 1st, the 7th, the 11th and the 12th months of the Islamic calendar). That is the right religion, so wrong not yourselves therein, and fight against the Mushrikun (polytheists, pagans, idolaters, disbelievers in the Oneness of Allah) collectively, as they fight against you collectively. But know that Allah is with those who are Al-Muttaqun (the pious - see V. 2:2).

The number of months, according to God, is twelve months—in the decree of God—since the Day He created the heavens and the earth, of which four are sacred. This is the correct religion. So do not wrong yourselves during them. And fight the polytheists collectively, as they fight you collectively, and know that God is with the righteous.