Those who disliked calling Muharram "Safar", and that postponing the months (al-nasi') is a practice of the Jahiliyyah

Imam al-Shafi'i (may Allah have mercy on him) said: I consider it disliked to call Muharram "Safar"; it should be called Muharram. And I consider it disliked to call Muharram "Safar" only because the people of the Jahiliyyah used to count the two months, Muharram and Safar, both as Safar, and they used to move Muharram and Safar forward and back; one year they would perform Hajj in the month of Hajj and another year in some other month, and they would say: If we have mistaken the place of the sacred month this year, we will get it right next year. Allah Almighty says: "The postponing (of a sacred month) is only an increase in disbelief" [Surah al-Tawbah: 37]. And the Messenger of Allah (peace and blessings be upon him) said: "Time has come round to its form on the day Allah created the heavens and the earth"; so no month is to be moved forward or back. And the Prophet (peace and blessings be upon him) named it Muharram.

It is narrated from Sayyiduna Abu Bakrah (may Allah be pleased with him) that he (peace and blessings be upon him) said: "Time has come round to its form on the day Allah created the heavens and the earth. The year is twelve months, of which four are sacred: three are consecutive, Dhu al-Qa'dah, Dhu al-Hijjah and Muharram, and the fourth is Rajab, the month of (the tribe of) Mudar, which is between Jumada al-Akhirah and Sha'ban." Then he (peace and blessings be upon him) asked: "Which month is this?" The Companions (may Allah be pleased with them) said: We said: Allah and His Messenger know best. The narrator said: He (peace and blessings be upon him) remained silent, and we thought that perhaps he (peace and blessings be upon him) would give it another name. He (peace and blessings be upon him) asked: "Is it not Dhu al-Hijjah?" We said: Certainly. Then he (peace and blessings be upon him) asked: "Which city is this?" We said: Allah and His Messenger know best. He (peace and blessings be upon him) remained silent, and we thought that perhaps he (peace and blessings be upon him) would give it another name. He (peace and blessings be upon him) asked: "Is it not the (special) City, that is, Makkah?" We said: Certainly. Then he (peace and blessings be upon him) asked: "Which day is this?" We said: Allah and His Messenger know best. He (peace and blessings be upon him) remained silent, and we thought that he (peace and blessings be upon him) would give it another name. Then he (peace and blessings be upon him) asked: "Is it not the Day of Sacrifice?" We said: Certainly, O Messenger of Allah (peace and blessings be upon him). He (peace and blessings be upon him) said: "Your blood and your wealth," the narrator Muhammad (may Allah have mercy on him) said: I think he (peace and blessings be upon him) said: "and your honour are sacred to one another, like the sanctity of this day of yours, in this city of yours, in this month of yours. Soon you will meet your Lord, and He will ask you about your deeds. Do not go astray after me, striking one another's necks, that is, killing one another. Behold! Let the one who is present convey this to the one who is absent, for perhaps the one to whom it is conveyed will retain it better than the one who heard it." Then he said: "Have I not conveyed?" But Imam al-Shafi'i (may Allah have mercy on him) did not narrate this text.
(b) Abd al-Rahman bin Abi Bakrah narrates from his father (may Allah be pleased with him) that he (peace and blessings be upon him) said: "Time has come round."

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].

Ibn Abi Najih narrates from Mujahid (may Allah have mercy on him), concerning "rafath" and "fusuq" [Surah al-Baqarah: 197], that rafath means sexual intercourse, fusuq means disobedience, and there is no disputing in the days of Hajj. He said: It is not a month that is moved forward or back; rather the month of Hajj has become clear, there is no doubt about it. This was because they used to drop the month of Muharram, that is, cancel it. Then they would say: Safar is in exchange for Safar. And sometimes they would drop the month of Rabi' al-Awwal and give it the name of Rabi' al-Thani.
The Shaykh said: There is a difference of opinion about the Hajj of Sayyiduna Abu Bakr al-Siddiq (may Allah be pleased with him) before the Hajj of the Prophet (peace and blessings be upon him), whether he performed it in Dhu al-Qa'dah or in Dhu al-Hijjah. Mujahid (may Allah have mercy on him) said that he performed it in Dhu al-Qa'dah, while according to some it was performed in Dhu al-Hijjah itself.

Abu Abdullah, Imam Ahmad bin Hanbal (may Allah have mercy on him), reports from Mujahid (may Allah have mercy on him) concerning "The postponing (of a sacred month) is only an increase in disbelief" [Surah al-Tawbah: 37]: They performed Hajj in Dhu al-Hijjah for two years, then they performed Hajj in Muharram for two years.
Then they performed Hajj in each month for two years, until the Hajj of Abu Bakr al-Siddiq (may Allah be pleased with him) fell in Dhu al-Qa'dah, in the last of the two years, one year before the Hajj of the Prophet (peace and blessings be upon him). Then the Prophet (peace and blessings be upon him) performed Hajj the following year in Dhu al-Hijjah, and that is when the Prophet (peace and blessings be upon him) said in his sermon: "Time has returned to its original state, as it was when Allah, the Lord of Might, created the heavens and the earth."

Humayd bin Abd al-Rahman (may Allah have mercy on him) said that Sayyiduna Abu Hurayrah (may Allah be pleased with him) said: Sayyiduna Abu Bakr al-Siddiq (may Allah be pleased with him) sent me, on that Hajj, on the Day of Sacrifice, to make an announcement at Mina: "After this year no polytheist shall perform Hajj, and no one shall circumambulate the House (of Allah) naked."
(b) Abu Abdullah said: The chain of al-Zuhri's hadith is good, and according to it the Hajj of Sayyiduna Abu Bakr (may Allah be pleased with him) was in Dhu al-Hijjah. Abu Abdullah said: Surah Bara'ah was revealed before the Hajj of Sayyiduna Abu Bakr al-Siddiq (may Allah be pleased with him), and in it is: "The postponing (of a sacred month) is only an increase in disbelief" [Surah al-Tawbah: 37], and in it is: "Indeed, the number of months with Allah is twelve months" [Surah al-Tawbah: 36]. Would it then be permissible for Sayyiduna Abu Bakr al-Siddiq (may Allah be pleased with him) to have performed Hajj according to the (old) way of the Arabs, when Allah had declared their practice to be disbelief?