Musannaf Ibn Abi Shaybah

Hazrat Hakam (may Allah have mercy on him) and Hazrat Hammad (may Allah have mercy on him) say that if a person says about his wife that for four months she is like his mother’s back to him, and four months pass, then this is Ilaa. And if he says that she is like his mother’s back to him and then leaves her for a year, then this is not Ilaa.