Al-Kinani used to call out during the pilgrimage season: 'Indeed, Safar al-Awwal is lawful,' so he would make it lawful for the people, and he would forbid Safar in place of al-Muharram. Then, when the following year came, he would forbid al-Muharram and make Safar lawful.
And the meaning of 'so they may agree' (li-yuwati'u) is: so they may align with 'the number of what Allah has forbidden.' They used to say: 'These are four [months] equivalent to four [months].'
Muhammad [Ibn Abi Zamanin] said: The postponement (an-nasi') in the language means 'delaying.' He says: It is their delaying of al-Muharram one year and forbidding another [month] for a year. Then, when the other year arrived, they returned it to being forbidden, so their postponement of that is an increase in their disbelief; and this is the meaning of what al-Kalbi said.
Surat at-Tawbah from verse (38) to verse (40).