Ibn `Umar used to say about the Ila (which Allah defined (in the Holy Book), "If the period of Ila expires, then the husband has either to retain his wife in a handsome manner or to divorce her as Allah has ordered."
Sahih al-Bukhari Book 68, Hadith 39
← Previous Hadith Allah's Messenger (ﷺ) took an oath that he would abstain from his wives, and at that time his leg had been sprained (dislocated). So he stayed in the Mashruba (an attic room) of his for 29 days. Then he came down, and they (the people) said, "O Allah's Messenger (ﷺ)! You took an oath to abstain from your wives for one month." He said, "The month is of twenty nine days."

Sahih al-Bukhari Book 68, Hadith 38 Next Hadith → "When the period of four months has expired, the husband should be put in prison so that he should divorce his wife, but the divorce does not occur unless the husband himself declares it. This has been mentioned by `Uthman, `Ali, Abu Ad-Darda, `Aisha and twelve other companions of the Prophet (ﷺ) ."

Sahih al-Bukhari Book 68, Hadith 40